Was Silver II in S6. After placement I got gold V ?

Soooo.... I saw a lot of people complaning how they won 9 of 10 matches and got downgrade from 2-3 rank. ive Never heard someone who actually won a few rank after placements.

So my question, How come it happened to me And how does the placement work exactly... Im so confused.

Also, I recommand playing vladimir, Maokai and swain (especially Swain). they are really good pick in bronze/silver even gold if you know how to trade to some extent.