Transplanting over another graft that has not grown

When a person gets a hair transplant, I know that it can take over 8 months and in some cases up to a year for 100% of the transplanted grafts to fully grow in (well, the ones that survive at least). At the same time I know that a person can often get a second hair transplant by 6 months which means that some of the grafts from 1st procedure might not have erupted yet. With that being said, what happens in that second procedure if a graft is transplanted into or near the same spot where a graft was transplanted during the first procedure and just hasn’t grown yet? Will it damage the first graft? Or will you just end up with two grafts growing from that spot; so basically like one big follicular unit?

I don’t believe that if one transplants over another hair graft, the second graft will add hairs to the first, making the follicular unit larger. A second follicular unit will arise in the area. Follicular units are controlled, I’m size, by the genetic mechanisms of the stem cells in these follicular units.