For numeric custom fields, you may specify minimum and maximum allowable values. These must be integer values.

If only the minimum is specified, then user-entered values are restricted to values greater than or equal to the specified minimum.

If only the maximum is specified, then user-entered values are restricted to values less than or equal to the specified maximum.

If both are specified, then user-entered values are restricted to values less than or equal to the specified maximum, and greater than or equal to the specified minimum.