How does mmr work?

Hey guys just trying to figure out how the %%%% does mmr work since my recent 30days wr is about 59% a the moment and even last 10 games are like 6-4 and yet i get +12 for win and -17 for lose so if anyone could bring some light into it for me it would be appreciated. :)
Report as:
Offensive Spam Harassment Incorrect Board