So I know all the things about IV’s and EV’s I have successfully bred a competitive eevee and have done the math on what it’s stats might be, so now my question is that how much EV yield I can get in the game. because my eevee has: 128 atk, 128 sp atk, 253 spd., 1 EV more than usual so how much ev yield is in this game. It’s suppose to be 128 atk, 128 sp atk, and 252 spd. All 510 Ev all in all.

The max total EV yield is still 510. Your second EV spread adds up to 508, not 510. Stats cap at 255 EVs for a single stat instead of 252 like they do in Generations VI & VII.

Did a bit more diggin into what you said it turns out that max EV in a stat is 255 but people do 252 because it will waste 3 EV in which 1 stat point is 4 EV’s, but thanks anyways really appreciate it.