Time Capsule and AirPort Passwords

I'm on 10.8.5 and use a Time Capsule for my router. When I'm in AirPort Utility I see 5 Tabs, three of which have passwords: Base Station, Internet, and Wireless. I know the passwords for the Base Station and my Wireless Network. However, in the Internet Tab, all the info here makes sense (PPPoE, my Account Name, etc) except there is another password here (which of course I can't see) but it's not the same number of characters that I would normally use for my passwords (it's too short). Therefore I don't know what that password is. I looked in my Keychain, but there was nothing there that specifically corresponded to that tab.

Any ideas on how to find what this password is in case I need it?

Time Machine is a backup utility and has nothing to do with your internet connection. You're referring to a "Time Capsule". Your title has been modified accordingly.