The "default" in your screenshot is likely the name of another wireless network near you...unless you also have another router with a network named "default".
If you can convince the owner of the other device to turn off his wireless router, you will not see "default" any longer.
All of the default networks for Apple products have a name like +Apple Network xxxxxx+, so this is not a wireless signal that is coming from your Time Capsule.
These screen shots are not from your Time Capsule.
Open System Preferences (gear icon) on the dock
Open Sharing
Check to see if you have Internet Sharing checked. If you do, this "network" is coming from your computer. Uncheck Internet Sharing