Delete brushes

Accidentally clicked several time Lol. That's like the police when they're like I shot the criminal by accident, and they have 20 bullet wounds.

Ok so change the Outliner to the Blender File, the twirl down Brushes and then right click and delete the brush you don't need.

It is a strange quirk of how Blender currently handles data though, so if you didn't find that intuitive then you're not alone. Blender's brush system is going to get an overhaul in the future, but exactly when is still up in the air.