What happens is, there is a formula, that I do not know but is in the spreadsheet I use, that calculates your pokemon's stats at a level based on species max, IV max, and its EVs. That's what determines your pokemon's stats, really. Once you get 4 EVs in a stat, the level up point will be applied when possible. (Eg: obviously 510 EVs vs 0 EVs wouldn't matter much at lv 6, so you'd see maybe a 1 point difference?)