Can someone explain how new ranked system works.

So I played 5 games out of 8 on mid. I believe I won 4 and I had normal kda more kills and assists than death as A grade and even one S-. First match I played I went A grade win but i got placed in bronze IV on mid. Now as I played 5 game out of 8 what happens when I will be done as I will play 3 more game I will have 8 out of 8 . So this will be the end of the placements and I will get different rank or I will be in same as I got on first midlane win bronze 3 as I got promoted after I won second game from 4 to 3.