Looks like he's logged into configuration to me.
Open Services, Telephony Services, General Settings, then click on Access Codes. Park Prefix will be at the top. As mentioned, it defaults to 1. That gives you 101-125 for the park slots. Analog devices always park at 125. Digital devices start at 101 and either work their way up if the mode is cycle, or revert to the lowest number if park mode is set to lowest. That is configured under General Settings, Feature Settings.