Leaver Buster Bull

OK So i did leave ONE ARAM game and the next day it said i had a 5 minute queue time so i didn't really care but as soon as i went into solo queue it says i have to wait 20 mins. This is bull crap and this isn't the first time either. I would like to know why even after getting out of the queue playing 20-30 games leaving ONCE and instantly getting a 20 min wait.