The poster upthread indicated an extra base damage amount for the lower lvl pets (2 lvls below mm) and so they factored in an extra 20% for first tier, and an extra 10% for for second tier pets (1 lvl below mm). I don't know if that's actually how it works, but it makes sense to me so that's where the "extra" damage is coming from.
It did get me thinking though, I had left that "extra" damage in my single target attack columns. I've edited those and now they should be right. I'd just like to say...WOW! You better bring a lot of friends to kill MMs with bodyguard up.