Look closley at your form element names, the first one is name correctly "ATCCheck[]" the second one is missing the square brackets. All of the checkboxes must have the same name "ATCCheck[]", the square brackets at the end are important for making it work.
Also, in the database search behavior, you have two search criteria set up, on for ATCCheck and the other for ATCCheck2, the one for ATCCheck 2 should be removed.