It is rolling month, which means you get back what you used on this day 30 days ago. So if you botted 12 hours a day, 30 days after that you would get 12 hours per day back.
So say you bot 12 hrs on may 1st, 2nd, 3rd. 0 hours on may 4th, and 20 hours on may 5th.
Then on
june 1st you would get...