Watcher said its because population numbers are calculated dynamically, e.g. a huge server with a 25k queue makes a server with a 2k queue a “medium” server by comparison. I have no idea why it would ever include queues in this calculation, but either way from his post it sounds like if it has a queue, it is not a medium server, it is full (at that time atleast).
I think the post was here, too bad they removed the classic general forum so now it doesn’t work…