No representation shall be made that a product or service is "blind-made" unless the manufacturer employs blind persons to an extent constituting not less than 75 percent of the total hours worked by personnel engaged in the direct labor, production, or manufacture of blind-made products or services. Direct labor production shall mean all work required for the preparation, processing, and packing, but not including supervision, administration, inspection, and shipping or the production of the materials from which the finished product is manufactured.