In Live View you can view your cameras as a single channel or multi-channel display. If you double click on a channel whilst in a multi-channel display it will open that channel in a full screen display, if you double click again it will revert back to the multi-channel display.
Display Modes
You can set the display mode from the Live View (right click) menu. This dictates which channel is shown or how multiple channels are displayed on screen.
Single Screen: Displays a list of all channels on the recorder. Selecting a channel from the list will display that camera full screen.
Multi Screen: Displays a list of all possible multi channel layout configurations. The configurations available differ based on the size of the recorder.
For more information on the functions of the Live View menu in the Operation section.