When the crane (cranes) is (are) being utilized to load or discharge cargoes or containers, necessitating the establishment of shifts for the operators and mechanics, and the lessee or stevedore finds it necessary to suspend operations during the overtime portion of the shifts, GPA’s operations department will be notified not later than 1600 hours (4:00 PM), the preceding date. If this notice is not given, the stevedore or lessee will be billed a minimum of seven (7) or eight (8) hours applicable stand-by time.