This is an issue I have encountered. It appears to be an issue with the sheet itself, as far as I can tell. The "damage" modifier is applied to both the primary damage for the weapon as well as the additional damage entries when the desired usage is to add to the total (not each part separately) or only the primary damage entry. For example., "Power Attack" applies a scaling penalty to attack rolls and a damage bonus of 2x that penalty's value. This should be applied once, so that if a weapon deals 1d6 slashing damage normally and has an added effect of 1d6 fire, the net damage should be (1d6+[power attack bonus]) as slashing + 1d6 fire. However, the "damage" modifier field is applied to both, yielding (1d6+[power attack bonus]) as slashing + 1d6+[power attack bonus] fire. The fields are "attack_bonus", "damage_bonus", "melee_damage_bonus", and "ranged_damage_bonus". Although the melee and ranged damage bonuses apply to the appropriate weapons, they still add to the "rider" damage as well as the primary in each case.