I Suck at Understanding MMR

So I am a big fan of the MMR rather than the weird leagues and divisions. But I really don’t understand how MMR points are awarded. But sometimes you lose a lot of points and often you gain very few. Like in this example:

11 points is not a lot. I thought that if you defeated someone better than you, you’d get a lot and lose a little. And the other way around too.
This is weird.