Donor grafts as high as 15,000, please discuss

In your assessment of my donor supply, you noted that I can bald to a Norwood 7 and still get hair. I’m not a NW7 but out of curiosity, I know different factors are involved, like head size and stuff but how many grafts would a Norwood 7 typically require for adequate coverage at an average transplant density? I know I’ve seen photos online from another doctor in California you’ve probably heard of or maybe even know (Dr. Umar), who specializes in the use of body hair grafts. Some of the Norwood 7’s he’s restored required over 15,000 grafts! One of the clients in particular, transplanted 9,000 grafts from just his beard alone! (how many follicles are even on a man’s face because he still was able to grow a beard, albeit just much less dense); the results were pretty impressive, regardless. Granted some of those clients requested really aggressive/ juvenile hairlines and had a lot of thin/single-haired grafts harvested from their back and legs which probably accounted for the need for a higher graft harvest