Is the true damage on top of his AD or build into his damage?
Here is the passive for reference:
(Innate): Corki's autoattacks deal 10% of his total physical damage before armor adjustment, as additional true damage to minions, monsters, and champions.
If I had 100 AD and shoot a target with 0 armor, does it then deal 100 damage hence 90% from AD and rest from true damage or does it deal 110 damage because of 100 AD+10% from passive?