Board Thread:Dragon City Gameplay Questions & Answers/@comment-11535585-20130731131655/@comment-10760902-20130731142402

the % different indicate the output value of that attack, not the base damage itself. This value depends on level of your dragon, rank.

So let assume you have a legend dragon (legendary, crystal, mirror) level 20.

Here is formula for output damage (by Andibad) Damage = floor((((level of dragon^1.5)+10)/250*Power of dragon+(2+a))*Rank Bonus*1.5*(0.85 + random number))

=> It looks very complicate, but I will show you Known values:
 * Power of dragon = 5600 (category 5)
 * Rank Bonus = 0 (assume)
 * Random number = 0.15 (maximum)
 * Level = 20

The formula has a fixed part, X = ((level of dragon^1.5)+10)/250*Power of dragon

=> Damage = X + 2 + A A is base power of the attack: Ratio of Damage(Legend Spell) / Damage(Rainbow) = (X + 2 + 2300) / (X + 2 + 1050)
 * Rainbow = 1050
 * Legend Spell = 2300

With X = ((20^1.5) + 10)/250*5600 = 2,227

Ratio = (2,227 + 2,302) / (2,227 + 1,052) = 4,529 / 3,279 = 1.38

This is the value +38% the system show you :)