MediaShout automatically adjusts text and pictures to appear best at the resolution of the main display screen. However, if no main display screen is connected when a cue is created or modified, it scales the content to fit the intended resolution entered here. If you build presentations while in single-screen mode, set the intended resolution to match the actual resolution of the main display screen the cues will appear on. This ensures that they display at the correct resolution during the presentation. 

To access these setting, go to: Tools > Settings > Screens > Main Display > Show Options > Intended Display Resolution.  The Intended Resolution that is set needs to match the resolution of the Main Display on the computer on which you are presenting.  See screen shot below.