Max. no. of marks and Min. no. of marks are options that you can select when defining a selection field or an indexed series of mark fields on a form definition. These options specify how many of the fields respondents are supposed to fill in.
In the Field dialog, click the Options tab.
Use Max. no. of marks and Min. no. of marks to specify the number of fields the respondent is expected to fill in.
Another way is to select Min. 1 and Max. 1 on the Standard tab of the Field dialog.
Any time you specify how many fields are to be filled in, discrepancies between what you specify and the actual number of filled-in fields must be resolved during validation or verification. The most efficient way to do this is if you also select options for resolution. What happens by default is that a validation error occurs.