GDNUM GDNUM allows the user to select grids by number in the following ways: GDNUM = range The first and last grid numbers in the range are separated by a -. If an increment is included, it will be ignored. GDNUM = list The grid numbers in the list are separated using semicolons. GDNUM = ALL All the grids in the file will be included. GDNUM = LIST All the grids in the file will be listed. The user will be prompted to select the grids to be included.