HI, here is a small artical from Mark Twin's Adam's Diary:
This day is getting to be more and more trying. It was selected and set apart last November as a day of rest. I already had six of them per week, before.
This day means Sunday, right? but six of them means what? it means Monday-Friday per week ?or Adam has had six Sundays totally, if so , why add per week?
It's a joke. It means that previously Adam did not work on six days of the week, not just on Sunday.