The "ejector" is, basically the part of the gun that the case smacks against and it kicks it out from under the "extractor" and out the ejection port. The extractor is the hook that pulls the case out of the chamber and holdsit against he breech face.
That appears, to me from the picture, to be ejector marks which are to be expected when soft brass, ring he cartridge, contacts hard steel, the ejector,with any amount of force. Some guns are more prone to it. Not a firm rule but I seem to notice it more in compact designs.
It is one of he reasons, along with bullet set back, that many people rotate the rounds in the magazine so they don't 're chamber, and unchanged the same round repeatedly. A small burr probably wouldn't cause a problem, but a chewed up rim increases the possibility.