The description says "Gain an additional wound", and also says that the number (which I assume is the x2, x3 number that follows the skill) means the times you have purchased the skill, so does this mean that SCx3 means that you have purchased the abiliy three times, and therefore you have +3 wounds? I would assume it works like this, but when you look at the Arch-Militant advances, the class comes with SC(no number) by default. Then, at level 2 you can purchase SCx3... without ever purchasing SCx2. Then for the next two levels or so you can purchase SCx2 various times. Then, does the number mean you gain 2 wounds for SCx2, and 3 for SCx3? Then, the SC the Arch-Militant starts with would mean he gains one extra wound?
All of this sounds confusing since the description says "gain an additional wound", not "wounds".