Use rollover time first

[Azirine]

If rollover time is available, it should be used first. For example, suppose you've set a time limit of 10 minutes in every hour, and from 0900-1000 you spend only 6 minutes on the sites in that block set. Hence, 4 minutes will roll over to the next hour (i.e., you can spend up to 14 minutes on those sites from 1000-1100). Now suppose you spend 12 minutes on those sites from 1000-1100. Of that 12 minutes, 4 minutes from the rollover should be used first, then 8 minutes out of the 10. Hence, 2 minutes should roll over to the next hour.