I'd love to help! It looks like you may have forgotten to attach the workbook.
I believe the solution you are after is:
I suggest making 2 calculations. One is your denominator at the region level (above) and your current calculation is your denominator at the total level.
FIXED will pass the same value at any granularity of your view. It is helpful for calculating percentages in this manner. You can also do:
This is the 'old' way of approaching this type of work. This works because it is comparing an aggregated mark (one little pane) against the entirety of the window. Unfortunately, this isn't possible with region. Fortunately, we have LOD calculations!