If your Didger project is projected in anything other than Unprojected Lat/Long, the numbers in the Project Limits and Scale dialog (Map | Project Limits) appear in meters. The Map Units in the X Axis Scaling and Y Axis Scaling sections are also in meters. Therefore, if you want 1"=2000', simply convert 2000' to meters (divide by 3.2808) and enter that number.

For example:
1" = 2000'
1" = 2000/3.2808
1" = 609 Map Units (meters)