At the time a refund is made, the marketing program committee shall file with the director a claim for the refund to growers that are entitled to such refund. If the director finds that as of the end of any marketing season the amount which remains to the credit of the marketing program committee is so small as to make impractical the computation and remitting of the pro rata refund, he may authorize the transfer of the funds to the then current marketing season for expenditure in carrying out the marketing program.