Berrnard, that is not pitting, it is pieces cooked on carbon. The Teslong is a digital image. I had a Hawkeye bore scope for a long time that is a true optical image, and showed what these little black spots were. The first time I used my Teslong, I was looking at the bore in my 6 BRX, and it showed what looked like a patch of black specks, and I could feel them with the bronze bristle brush. I got the Hawkeye out and examined the area and it was carbon. There is no rhyme or reason as to why patches or pieces of carbon will stick to a place in a barrel.
It takes a while to figure things out, but you will get there.
I would urge you to create a "file" on each barrel. If you keep records on the number of shots fired or NOT, you can monitor the progression of the wear. The pattern of wear will amaze you over time.