The established quitting time for each operational unit shall be strictly enforced. Where employees are required to ring a time clock, they shall be permitted to ring out and leave the premises not more than three (3) minutes prior to the established quitting time; provided, however, that where there are more than sixty (60) employees per time clock, six (6) minutes shall be provided. Clean up time for the employee's tools and equipment, work area, and person shall be negotiated from operational unit to operational unit, between the individual unit, and the Union and the Department of Human Resources.