An eyebrow isn't a small scalp — the angle is completely different.
An eyebrow is not a small scalp.
Scalp hair grows at a near-vertical angle. Eyebrow hair grows almost flat against the skin, and its direction shifts along the brow: upward at the inner end, forward through the middle, then down and outward at the tail.
That is why the work is done one hair at a time, with the angle and direction decided individually for each one. Any error in angle shows immediately, because the brow sits in the middle of your face.
One more thing that matters: transplanted brow hair comes from the scalp, so it keeps growing and needs trimming.
Results start showing around month four and settle around month eight — faster than the scalp, because the graft count is much smaller.
What does your case actually need?
The video explains the general rule. The number that applies to you is settled after an examination — the grafts your case actually needs, not a figure quoted before we have seen you.