Your total hair count is the same before and after. Only the layout changes.
Understand this before anything else: a hair transplant does not create hair.
No new follicles are grown. What happens is that follicles are moved from an area with surplus density to an area that is empty.
So the total amount of hair on your head is the same before and after. What changed is how it is distributed.
Once you understand that, your expectations settle into the right place. You are not going back to the density you had at twenty. You are going to get coverage that stops the bald area from reading as bald. That is a good result — provided your donor area is spent wisely.
Anyone selling you the hair you had at twenty is selling you something that does not exist.
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.