On or before the 16th day of each month (except as provided by section 21.92 of this Part), the commissioner or a person authorized by him shall direct the fiscal agent to make payment out of the equalization fund to each marketer operating a pool plant and each collecting cooperative which has arranged to make the reports and payments with respect to the milk of producers, the amount by which the value of milk computed pursuant to section 21.64(b) exceeds the value computed pursuant to section 21.64(a) of this Part. If, at such time, the balance in the equalization fund is insufficient to make all such payments, the commissioner shall reduce uniformly such payments and shall direct the completion of such payments as soon as the necessary funds are available. No marketer who, on the day he is required to make payment pursuant to section 21.60(c) shall be deemed to be in violation of such section if he reduces his payments to producers by not more than the amount of the reduction in payment from the equalization fund.