Does the +10 Armor from the Invulnerability potion mean that you would get additional to the existing armor, is the +10 the total? For instance if you have an armor that is +2 and a shield that give you +1 do you have +13 armor?

leoj said:

Yes, that is what + means...

Note that a shield doesn't give you +1 armour. It cancels/prevents one wound.