Loss of 20 LP due to people that DC or AFK in game. (Ranked)

Hello! I played a ranked game today and lost due to a double afk. I normally lose 16-17 lp per game, but for some reason this game dropped my lp by 20. It's not a lot, but why the 3 lp difference? Another person said he lost 23 in the end game lobby (because of privacy reasons I won't be giving his account name) but on op.gg it says his mmr is quite above average and his winrate is well above 50%. I want to know why I lost more lp in a really unlucky game, because the 3 extra lp put me in an odd lp number that would require me to play 1 extra game than I normally would to get into promos.