Oh! okay, I thought it was per use. And thank you for pointing this out.
I’m surprised that pulling out is anywhere near 96%, but in that case “perfect use” seems kinda arbitrary. Or maybe it means something like at the first relevant sensation the guy pulls out. IDK how you measure that scientifically though. I think it’s highly likely that the vast majority of pulling out is imperfect, though, so it’d be useful to have data around actual effectiveness based on reports of primary contraceptive method (I haven’t looked).