These numbers are used to indicate callers who you want to be allowed to call you as normal even when you have 'do not disturb' on. This does not include group calls which are not presented when you are in 'do not disturb'.
Your system administrator can configure whether you can access this menu.
To do this during a call, press the PHONE key and then press Features.
To add a number, highlight Add Another. Dial the number and press Add.
If your system uses an external dialing prefix to make outgoing calls, add the prefix when adding an external number as an exception.
To remove an existing number, highlight it and press Remove.