By default, check boxes use numbers to represent values in the form data. The default values are “1” for On, “0” for Off, and “2” for Neutral. You can change these values to match existing values in a data source or to provide more meaningful terms related to the purpose of the check box in the data file.
4. If On/Off/Neutral was selected in the Field tab, in the Neutral Value box, specify the value of the check box’s Neutral state in the data source.