Bronze 5 from 8 Wins in Placement--> Error? (read explanation)

Hi guys, I ended as Bronze 1 in season 5, and during the preseason still left off at bronze 1. I won 8 out of my 10 placement games, and carried (S or A grade) for 6-7 of those games. However, I was placed in bronze 5... The reason I know this is an error is because I went back on Lolking after my rank was given, to see if I was just tanking my mmr last season. But, my Lolking score, which was +30 had dropped to a drastic -244 after I finished my placements. This tells me that before my placements my mmr was going up because I was winning, but somehow the placement gave me bronze 5 and I dropped 274 in my Lolking "mmr" (244+30). Note: although Lolking doesn't show mmr you can assume correlation between mmr and the Lolking score. Isn't this a ~~ "schism in the system" [zombie-brand-mindblown]