Rank placement??

OK before the start of the season 5, i was in my GOld promo. I win 6 outts of 10 of my placement games, yet i got placed in silver 4 . how in hell am i placed in silver 4? I have never been silver 4 in my life. And to add in my was playing other gold III and platy players in my promo games. I am really confused and very very frustrated.