the PT3 website has an explanation of what goes into the EV line if you're interested enough. basically, it determines how much you would in on average based on your equity when the money goes all-in before the river. example: you and i get all-in headsup on the turn in a 5 millon dollar pot. my equity when the money goes in is 90%, and yours is 10%. my EV is 5000000 * 0.9 = $4500000. so my EV line will go up $4500000 in that hand, regardless of whether i win or lose the pot.

realistically, you're best off to not even look at it, ever. it's just a distraction. keep making +EV plays over enough hands and you can just look at your actual winnings line. there's no use fixating your mind on what "could" or "should" have been. it doesn't change the fact that you have x amount in your online account. and can potentially be a source of tilt.