This should probably be in Units Millimeter and not Inch. What happens is that your design shows extents over 300" (which is about 10 meters long!). My guess is that you may have imported a DXF file into FAB 3000. If yes, make sure to tell FAB 3000 that your DXF file contains units "Millimeter"... because DXF does not have any units so you must tell FAB 3000 what units to use.
After importing as Millimeter units, you should be easily able to export as Bitmap.