The text states that animals with the bioelectricity trait deal an additional amount of damage with the stun trait.
So, if an animal deals 2D and has Bioelectricity +3, I guess it will work like this: It deals 2D +3 while only the last 3 are STUN. So if it rolls 7, it will deal 7+3 = 10. Someone who has armor 8 (improved cloth) will take 2 damage and be stunned for 2 rounds. Effect will add to the normal dmg, not the stun.
I.e. when accounting for armor, first comes the normal damage and later, the stun damage. Of course, this is only my interpretation of the rules.
So, if an animal deals 2D and has Bioelectricity +3, I guess it will work like this: It deals 2D +3 while only the last 3 are STUN. So if it rolls 7, it will deal 7+3 = 10. Someone who has armor 8 (improved cloth) will take 2 damage and be stunned for 2 rounds. Effect will add to the normal dmg, not the stun.
I.e. when accounting for armor, first comes the normal damage and later, the stun damage. Of course, this is only my interpretation of the rules.