Obviously, if you take a day out of the five-day sitting week—on Fridays the House sits for 4.5 hours from 10 to 2:30—that lost time, if you want to put it that way, could be made up on the four other days.
Historically, when the House has adjusted its sitting hours, it has tried to make sure that the number of sitting hours per week either increased or at least didn't go down. That's what was done previously. You could conceivably add the time lost for the various items at different times in the week.