For table calculations, the level of detail needed to correctly calculate the value must be in the view. However, the view can be further modified to make it look like day hasn't been added. For starters, you can check out Computing a Table Calculation by a Dimension Not Present in the View | Tableau Software
It looks like on the various days of the week the threshold will switch between above/below. So I wasn't sure if a week has both above and below on different days, which threshold should be used for the whole week.
Meenu has a great calc for finding the week of month in this post How to display week number by Month
Hope this helps