Addition of costs, etc., to certificate and payment by certificate-holder of purchase money in excess of the amount of certificate

Upon the hearing of the petition referred to in rule 53, sub-rule (6), the costs of execution, including the poundage fee shall be added to the certificate; and in cases in which the amount of the purchase-money exceeds the amount of certificate and such costs, the certificate holder-auction-purchaser shall pay to the Certificate Officer the sum of 25 percent, on the balance of the purchase-money after deducting the amount of the certificate and of such costs, and shall pay the balance on or before the fifteenth day from the sale in accordance with rule 69.