If the Client is using more than one monitor, then additional options will appear in the toolbar enabling to switch view from monitor to monitor or to view all monitors at once:
Show Monitor 1
Click "Monitor 1" button from toolbar to set view region on monitor N1.
Show Monitor 2
Click "Monitor 2" button from toolbar to set view Region on monitor N2.
Show All Monitors
Click "All Monitor" button from toolbar to view both monitors at once.