How do we mark an effort which has been billed? / #4472

First of all, I must say this application is great, especially the use of WIKI to link information together.

I'm using Efforts function a lot to track my time, at the end of the month, I will consolidate all the time and bill customers accordingly, but I'd like to know, after the effort has been billed, do you change the status to "Balanced"? Or "Discounted"? I don't understand what these two status are for. Anyone?