Can't really tell, maybe it has a small rough part right there. Have you taken the gun down? I had a similar rough place on my PT-140 on the top, so I took the gun down and took a file and just barely hit it a little to smooth it out. Seems to have helped, mine had that much after a 100 rounds or so till I smoothed it down.
Well said MOONDAWG, this rub mark could be caused by burrs, excessive shooting, misalignmment of slide, debris ...... The best thing to do is to break it down, clean it really good and then look for any sharp edges or burrs and smooth them out. Does the rest of the gun insides, ramp etc look good?