To test this out, I created a brand new server, unmodified...a complete virgin.
I went in and added 10 bots.
Server slot count showed 1/10 from counterstrike server listing. This happens with and without the bot_join_after_player 0 setting as well.
Here are some screenshots for you to see what I am talking about.
1:
http://durkastan.com/pics/counterstrikewindow.jpg
As you can see, the highlighter server shows that it is only a 10slot server. This is how it appears in the server listings.
2:
http://durkastan.com/pics/counterstrikeservermenu.jpg
This one shows that the server count is really 20 slot, but only if you go into the server detail view.
3:
http://durkastan.com/pics/serverstatus.jpg
Screenshot from the control panel, once again showing that the server is indeed a 20 slot server.
So the server is showing up in the server listing as a 10slot server, when it is in fact a 20slot server, confirmed by both the server detail view and control panel. That is why I am thinking that this must be an update issue when they converted to OB, as this has occurred on each server I have tested it on.