(This item pertains to the check boxes on the General tab of the Setup Options dialog box. You can open it through the F5 key or through the Edit | Preferences | Setup menu option.)
The Use ONLY Priority Surfaces for the Find Nominals During Scans check box causes PC-DMIS (during measurement routine execution) to search for nominal values for a scan's measured points on only the priority surfaces set in the Edit CAD Elements dialog box.
See "Editing CAD" in the "Editing the CAD Display" chapter.