In OS X Server.app, what's the number in the app icon? I have Server.app on 10.7, and when I start it, I get the neverending beachball, and in the Dock, the Server.app's icon has a red number in it, which is continuously increasing.

What's the number mean?
It means the number of alerts you have. There are several things that can prompt it to show alerts in Server.app, such as software updates available for the server, a volume unplugged unexpectedly, etc.