how much lp do you lose for dodging ?!?!?!

there i was looking at my profile , won my last 3 ranked games with yi jg including one game a irelia went afk since level 3 and reconnected about 2 minutes before me and my team won the game , then i decide," oh lets do ranked again !" in champion select screen a guy who wasnt hovering zed says i banned his zed, and he is a one trick and cant play , bot says they are duo and wont trade zed, i kinda feel bad for what happened and since i won 3 games i tell them ill just dodge and go out for some food , then after not picking my champion i go back to my profile to check my lp -3 , how do i win 3 games and dodge 1 time and end up with less than 0 lp , 3 negative lp score how is this even possible, i even carried one game with an afk i dont remember how much i had before but im sure that for winning 3 games i shouldnt end up with negative score with 1 dodge, what is this