Servers are incorrectly open displaying slots. Example being -30 and -68 which I see right now. Maybe the servers never register when people leave?
I confirm this as well. Also unable to join any servers, even ones with non-negative numbers listed. Not behind any firewall here.
The negative numbers seem to be for every failed connection. I tried to connect to a server with 0, failed, then next time I saw it on the list it was -1. I did this a few more times to test and it went down by 1 each time.