It's not that hard to understand. Look at the spreadsheet.
I have looked at it. My count is right.
Saturday's posts got included in the last week while they should count for this week.

But whatever, I make more than 40 posts anyway.
It would have been much better to specify that you were referring to posts made on 1 March, not 22 February. The 1st March posts didn't count for last week in my case.