ItemAdditionalDamage special bonuses (Bonus2)
Bonuses 67 and 68 don't have their damage part (MM8 issue).
'(10-20) ... Damage' should be implement as Bonus2.
There should be an event checking for additional damage bonuses (like it was done for double damage bonuses, but with only one bonus possible).
Note: Currently items that have double damage via OnHitEffects (see ExtraArtifacts.lua) doubles additional damage only, not the base one. ItemSpcBonuses work correctly (as in vanilla).