Please explajn this rating system to me

So i have it screen capped in photos but i cant post pictures here apparantly but you can go ahead and look for yourself. Basically me and a buddy played the ranked slayer playlost together. We played all 10 matches together and played against the same exact people. I performed better than him in all respects. More kills than him and less deaths than him. He placed somewhere in platinum while i placed somewhere in gold. How does this make a lick of sense? If u dont believe me u can go ahead and look up andariei which is MY gamertag. His is Dead Poets Oath so go ahead and check it out. Explain this to me in a way that i can understand

Duplicate Topic