How do Placement Matches even work?

So I decided to try out doing ranked right, did my placement matches and I thought I did pretty freaking decent.

I went: Game 1: 10/2/3 Loss Game 2: 14/2/11 Win Game 3: 8/0/10 Win Game 4: 13/5/13 Win Game 5: 4/3/2 Win Game 6: 15/7/16 Win Game 7: 10/5/6 Loss Game 8: 8/3/11 Win Game 9: 15/1/5 Win Game 10: 6/4/16 Loss

But yet.. I only somehow placed Bronze 1?! I'm not too sure I understand, I played much better than that and even had very high cs, kda, and winrate, achieveing at least 6 S- or higher games, but thats only Bronze 1? Can someone help me out here?