Is 600 grafts enough for a normal hair density?

A hair transplant in one session is never normal hair density for the size of the area you are transplanting. You can see it by looking at the lack of density of the grafts, but in your case, the area covered could have had more grafts. I don’t like the line-up of the hairs that were transplanted as they should have been more randomly placed. Your grafts were placed far too orderly for me but another hair transplant with more random placement of the grafts will solve this problem and give you more density. If this is the way your doctor does his transplants, I would look for another doctor.