Determining MOA of Impact rail

Wanted to ask the group about this but I picked up a new M3 from Bullet Central some months ago and I wanted to get some more adjustment out of my PST Gen2 and noticed I had about 8 mils to play with so I was thinking of buying a 20 MOA one piece mount. After spending weeks looking for used mounts on the powderburner forums I starting wondering about the top rail on this air rifle because it’s supposed to be 20 MOA. I set the M3 up this morning and ran a level down the barrel and then along the rail and both were parallel, which surprised me as I expected the top rail to have a downward cant.

My understanding is all the M3’s came with the 20 MOA rails so am I measuring this wrong, because I’ve got about 14 mils of elevation and 8 mils to play with on a 58 yard zero.