For the 6x12 (all I use it for) I took a processed rolls paper, took the back off the film back and lined it up as if running film through. marked the paper as if shooting and found that for 6x12 the frames are: 1,3,5,9 and 11. for some reason the #'s are upside down also. Don't know why but it works. As far as the ground glass, mine aligns perfect with the 4 little horizontal F brackets.