It's per 100 hands dealt. You can roughly keep track of this yourself by coutning how many times you are in the blinds.

I think when people talk about BB for NL, they are talking about 2xthe big blind(someone correct me if I am wrong). So for the $2 buy in NL, that's $ .08. I didn't say 1BB/40-50 hands for the $2 NL, I said $1-2 per 40-50 hands. This is around 20BB/100. I think 20BB/100 is quite possible at the $2 NL. 1BB/100 is only like four cents an hour.