If a label was assigned to the System Custom Fields Table 1, 2 or 3 field, you will then enter the choices in the corresponding table. For each choice you would like the User to be able to select from, create one record in the corresponding setup table. The number of records you may enter is unlimited.
The entries made into the Custom Fields Table 1, 2, 3 are the choices that will be available in a drop down menu in the System Information record, on the tab labeled Custom Fields.