Where a guarantor in writing guarantees the payment of money and credit thereafter to be extended, which guaranty is a continuing guaranty and by its terms limits the credit to be extended to a fixed sum and the creditor extends credit in excess of the amount stated in the contract of guaranty, and the debtor becomes insolvent and in course of admistration of his estate by the court a dividend is paid upon the entire claim of the creditor, the dividend so paid should be applied pro rata upon the secured and unsecured portions thereof.