User blog comment:EloHell/William - Dragon Slayer/@comment-123.118.123.189-20121130120551/@comment-4022742-20121130132911

As far as I read it the bonus true damage is based off of armor and magic resist, that value gets amplified by the percentage of missing health, so you'd get the math as:

Armor + Magic Resist * (missing health * amplification) = total bonus damage.

140+80*(80*1)=396 true damage on level 16...