Explain this....

So me and 2 friends decided to do our Ranked Twisted Treeline placements together. All of us finished Silver 4 in Ranked TT last season. We did all 10 games together and scored an even 5-5 record. Somehow though, I got Bronze 1, one of us got Bronze 2, and one of us got Silver 4. I do not understand Riot's elo and placement system. It makes no sense.

Other factors, I had the highest Solo-Duo rank out of us, and the one that got the Bronze 2 had the highest Flex rank out of us. Not that that should matter anyways.