User Activity Monitor : Monitoring Settings : Options : Video resolution
  
Video resolution
The Video resolution option allows the administrator to set the output resolution for the screen video recorded by the DeviceLock Service. This can be the resolution of the screen being recorded, or a different resolution selected from a list in the option setting.
Double-click this option to view or change its setting in the dialog box that appears:
Resolution - Select the desired output resolution from the drop-down list for this setting.
For the output resolution to match the resolution of the screen being recorded, select Native from the Resolution list.
 
Important: Recording maintains the aspect ratio of the screen being recorded, so the height or width of the resulting video may differ from that specified by the output resolution. Typically, the width matches the output resolution, and the height is calculated so as to preserve the original screen aspect ratio.