The math and apparent reality don't add up! There's no way that toilet would be 1-3/4" from the wall IF the rough-in is 13.5" and the 12" rough-in was used. Normally, when everything is perfect, there's about 3/4" behind the toilet to the wall. So, if your rough-in is truly 0.5" short, you'd subtract that from the 'normal' clearance, and it should sit 1/4" from the wall IF the 14" adapter was used and the rough was really 13.5".
The rough-in is measured from the finished wall to the center of the rough-in (not the baseboard).