If the marketing order affects directly only producers of a particular commodity, the members of the advisory board shall be producers. If the marketing order affects directly only handlers of a particular commodity, the members of the advisory board shall be handlers.
If the marketing order affects directly both producers and handlers of a particular commodity the advisory board shall be composed of both producers and handlers. The number of producers or handlers upon any such advisory board shall be of such number of producers or handlers as the director finds is necessary to assist properly in the administration of such order.