riot jacked 9 lp from me

so i just got promoted to plat 2 and then won a match (1930 mmr, average for p2 is 1950) and got 11 lp (which would be like, 9 divisions mmr lower than p2) instead of 20 rito pls? also my teamates got it aswell screenshot: https://imgur.com/a/Ti8ZV