bb/100 is big blinds per 100 hands. Whereas, ptbb/100 is big bets (big blinds * 2) per 100 hands. PokerTracker will say bb/100, but it actually means ptbb/100, unless you have changed it.

Therefore, if you are running at 3ptbb/100 at 100nl. THat is the same at 6bb/100, which evens out to $6/100 hands. Playing around 5-6 tables you can get in 400 or so hands an hour, for around $24/hr. As jyms said, I'm sure it's a good deal more with RB/bonuses.