No minor may be employed for any five-hour period without one interval of at least 30 minutes for meals. If the period of work before the interval exceeds five hours by less than 15 minutes, that difference is not a violation of this provision. The interval may not be included as part of the working hours of the day. The interval must be 30 minutes. Any difference in length of the interval less than 15 minutes is not a violation of this provision.