Question about lp and mmr

So I know that you gain lp depending on your mmr compared to the mmr you should have (you get +20 and lose -16 if you have a higher mmr than your division and vice versa) but doesn't everyone in your game gain/lose the same lp as you? So if im in a dup queue with someone that has high mmr and you have low mmr it gives you the same lp so is it like the average lp you both should have got or what exactly?