The system as I understand it is as follows, but let me know if it's been changed cause it could be outdated:
When rolling for an attack, your penetration is checked vs the targets armour for the type(s) of damage you're doing. If its less than their armour, you deal 30% damage, if its equal or greater, you deal full damage, and if it's double or more, you get a 30% bonus.
Presuming the system hasn't been changed, is that 30% bonus damage additive or multiplicative?
Are the mechanics the same in reverse, when someone hits you?