I also didn’t know this before . Few days ago i was going through revenue section on my profile and i was thinking what does this cpm means which in brackets I mentioned in picture you can see. 

I think most of new members also dont know about this . So i want to share this info .

When someone buys our post our revenue are distributed into half to each other . Same like this , cpm also becomes half to each other . But if you get your post back through buying , remaining cpm will show on the revenues you get after owning your post from the buyer . 
I hope its clear 🤨