FFA CSR increase/decrease

I’m currently at plat 4 for FFA----noob I know xD
But I want to ask if its only the top 3 positions that increases the CSR while placing the bottom 3 would decrease my CSR?

Plat 4 isn’t bad, but for me I always get a CSR boost, it depends who you beat, at the start of the season I got first about 60% of the time but now I tend to come 4th. If you’re squaring off against diamond though is still goes up