@dbooks.org is interested in rewarding its users even after the 7 day payout period might have lapsed. For now, the 20% has a sharing formular. There has been debates on the sharing method to use and we have decided to come up with a formular which would be explained in our next update post. Later, when we begin to receive delegations, in a bid to incentivize our delegators (if they are interested- the option would be made available), we would have to adjust the sharing formular.
The 20% is gotten from each post in a chapter.