Just took my Glock 30 out for the third time and it shot great. 200 rounds and not a jam. When I came home I cleaned it and I noticed something. On the inside of the slide, towards the front, I noticed some markings. I'am not sure if they were there before, but I noticed them now. It's a little rough; whereas, the opposite side is smoother. I know the picture isn't that great, but it's hard to get an angle on it with good light. I tried to brush it off with a plastic brush, no luck. I also took the tip of a jag and tried to scrape it a little thinking maybe it was gun powder residue, no luck. It's definitely stuck on the slide. The two blue circles are where the area in question is. Is this just an area that wasn't finished well. Or is it something to worry about. Can it compromise the strength of the slide? Any suggestions?