If you're referring to 19/8/2, or something similar, it's VP$IP/PFR/AF. That's volume put $ in pot, preflop raise, and aggression factor, respectively.

VP$IP is essentially the % of hands you play, PFR is how often you raise preflop, and AF is the number of times you bet/raise divided by the number of times you call.

These stats are all available in poker tracker and PokerAce HUD.