if those are the only 2 places that the shared variable is being used, I would try creating a new section for groupHeader 1, and move it to the top...making it the new groupHeader1a. Then I would place the subreport in the new groupHeader 1a, and run the report and see if the discrepancy still exists.
also as a note, you don't need Initial_Denom:=Initial_Denom, just Initial_Denom in the display of the shared variable.
The other thing that you could try, would be to double check the values in the subreport or manually look at the data and see which number is right (hopefully 1 of them). This might also guide you to what is going on in the report.
while I don't think is happening, if you displayed a total before the last grouping was in, you would see a difference, and yet the report would be complete correct, the difference being just a logical choice of when to view the values.
HTH