hi, friend. What I understand is that this statistic measures the percentage of hands played in which a player raises from back positions (CO, BU, SB). I hope it helps you, greetings
ATS (Attempt to steal) is a measure of how often a player tries to steal the blinds from the CO, BTN and SB positions.
CO ; cut-off (the seat to the right of the button)
BTN ; button
SB ; small blind