Elo score makes no sense, there's something off here

[Suoivax]

How much you win or lose is dependent on the ELO of your opponent.

I know that, in theory. But how do you explain the fact that I often find people with 150 playing like a 300?

ELO doesn't stop a 300 from pairing up with a 150, what I'm saying is if you beat someone with an ELO of 150, you're not gonna get many points, but if you beat someone with an ELO of 800, you're gonna get a lot of points.

That's why 6 wins and 6 losses doesn't mean you end up with the same ELO you started at.