u/Fit-Extension-3431

I just had some gsa cc’s graded by cacg the photo shows al the same date (1881-cc) why is the ms-62 showing pop 1 and the ms 63+ is showing pop 8? Also the prices are pretty much the same across 3 grades (61-63+) (ms61= 1k ms63+=1150??) any insight would help, I’m very new to grading coins and registry’s in general.