When it comes to weapons your level affects how much your weapon attribute scales your damage as well as your critical chance. A critical hit sets your base damage to the max damage of your weapon * 1.41 (or 1.1 in the case of scythes).
When it comes to spells your level determines the baseline armor level that the enemy would need to break even on damage. The damage they take is scaled according to where their armor level is relative to it. So, a charr shaman has (according to the wiki) 23 armor vs fire. A level 7 ele with 10 fire magic would see the flare description say it deals 50 damage. The breakeven point for this ele - three times their level - is 21AL. The charr has more armor than that so that 50 damage gets scaled down. When the ele levels up their breakeven point goes up to 24AL which is higher than what the charr has, so flare would get scaled up in damage.
When it comes to weapons your level affects how much your weapon attribute scales your damage as well as your critical chance. A critical hit sets your base damage to the max damage of your weapon * 1.41 (or 1.1 in the case of scythes).
When it comes to spells your level determines the baseline armor level that the enemy would need to break even on damage. The damage they take is scaled according to where their armor level is relative to it. So, a charr shaman has (according to the wiki) 23 armor vs fire. A level 7 ele with 10 fire magic would see the flare description say it deals 50 damage. The breakeven point for this ele - three times their level - is 21AL. The charr has more armor than that so that 50 damage gets scaled down. When the ele levels up their breakeven point goes up to 24AL which is higher than what the charr has, so flare would get scaled up in damage.
Ty for explaining 
but what are the difference in this Special Case:
14 Marks Ranger lvl 19 crit hit with nevermore bow (15-28) without a Skill to a lvl 8 caster charr in pre
To
14 Marks Ranger lvl 20 crit hit with nevermore bow (15-28) without a Skill to a lvl 8 caster charr in pre
= Difference of 5 DMG, of 10dmg? No idea 
Same with flare....
14 fire ele lvl 19 flare to a lvl 8 caster charr in pre
And
14 fire ele lvl 20 flare to a lvl 8 caster charr in pre
= Difference of?
Would be very Happy If Somebody could Help me ty much
As far as I can see on that page, the damage of an actual critical hit is not different between lvl19 or lvl20. Level only affects non-critical dmg, and critical hit % chance, not critical hit dmg. So if enemy armor lvl, bow attr level, bow dmg & modifiers are all the same, your critical hits at lvl19-20 will deal the same dmg.
In case of spell damage, the only thing that matters is caster level and enemy armor level, not enemy exp level. Your example is worked out (not for lvl 19-20 but for lvl6-7) further down that page... There is no place in the formula for enemy lvl, only for enemy armor lvl (60).
Oh haha sorry, didn't realise you were asking for someone to literally type the numbers into a calculator for you.
Its to complicated for me
Spell damage is simple. Under those circumstances the damage should be 106 at level 19 and 112 at 20.
As far as I can see on that page, the damage of an actual critical hit is not different between lvl19 or lvl20. Level only affects non-critical dmg, and critical hit % chance, not critical hit dmg. So if enemy armor lvl, bow attr level, bow dmg & modifiers are all the same, your critical hits at lvl19-20 will deal the same dmg.
The page doesn't make it clear, but the attribute level part in the critical hit formula needs to be adjusted according to the attribute threshold, which does apply character level. Having said that, the character level is halved so if it's rounded up (which I assume to be the case but might not be) there won't be a difference in crit damage between levels 19 and 20.
Assuming the 15% damage bonus is triggering and the bow is customised, in addition to the stated circumstances, the bow crit should deal 106 damage (not a typo - it's incidentally the same as the level 19 flare damage).
Back in the day Chthon built a damage calculator which you can find here: https://archive.guildwarslegacy.com/06/06%20Commun…ulator.001.html
It's only for weapons (presumably because spells aren't complicated enough to bother) and it assumes you're level 20, but it'll tell you plenty. It confirms the 106 crit damage I calculated above, plus it shows the average dps. At level 19 your crit chance will be lower and thus your average dps will be lower. To save you a minute I've screenshotted mine, though obviously if you want to play around with it (maybe you're /W for frenzy or something) you'll need to set it up yourself.
Ty very much
I made an error with the calculator - I overlooked the level box because I thought it was only used for estimating the armor level of the target. Setting it to 8 results in it calculating a 100% critical chance, but with an additional message that says "Note: Critical hit chances greater than 66% are subject to an unknown (presumably) asymptotic limiting function that prevents them from ever reaching 100%. Your actual chance to critical hit is slightly lower than the results displayed."
Also, I forgot to mention that attacking from a higher elevation than the enemy increases your damage, though I've never seen anyone attempt to quantify it or figure out how to calculate it.
I think we're looking at this the wrong way. I think the threshold isn't rounded at all - there's no need for it to be. You can't have half attribute points, so odd levels where you get .5 thresholds are functionally identical to the level below. So at level 19 (threshold 11.5) it takes 11 for the under and 3 for the over, which is the same way it turns out at level 18. Inputting 11.5 and 2.5 doesn't make sense. What would be getting rounded is the under (rounded down) and the over (rounded up).
It is indeed a 6 point difference in damage, though in practice it probably isn't relevant. Against a 220 health enemy it should be a two hit kill either way once you factor in the elevation bonus and/or ignite arrows and/or a charrslaying mod. Maybe it makes a difference if you want to one shot them with dual shot, or if you take the ranger and warrior charr into consideration.
