50 k sample is req. like badger said.

6max 3-10 ptbb/100 is good 10 being really good.
9max 2-6ptbb/100 2 being good and 6 being really good.

The way i use ptbb/100 is not how good i am vs other ppl but every 50k sample size i want to beat the ptbb/100 from my last sample.