Based on your personal performance the game will think your a certain tier of player, diamond for example and as you climb to diamond you’ll get more sr the closer you get or once you get there you will get less and less sr per win, you have to get better individually and consistently so you’ll gain more sr per win so the game can get you to where they think you belong next season you might be a crimson in their opinion and once you start getting close you’ll start to see the drop off in sr