To quote directly from the blog:
Am i mistaken are are you saying that the server transfer ratio is one to one where no other origin server will transfer to the destination sever or another origin server?
So, in some cases, multiple origin servers will be assigned the same destination server. The end goal is to have destination servers with higher populations, and that may require sourcing from several origin servers.
In some cases, a large number of origin servers will be eligible to move to a single destination server. In others, very few origin servers will be transferring to existing high population destination servers.