Should the assessments in any special assessment roll prove insufficient for any reason, including the noncollection thereof, to pay for the improvement for which they were made or to pay the principal and interest on the bonds issued in anticipation of the collection of such assessments, then the Council shall make additional pro rata assessments to supply the deficiency, but the total amount assessed against any lot or parcel of land shall not exceed the value of the benefits received from the improvement.
Should the amount collected on assessments prove larger than necessary by five percent or less the amount of the original roll, the Council may place the excess in any of the funds of the City, but if such excess shall exceed such five percent, then the same shall be credited pro rata on the assessments against the several parcels of lands according to the amounts thereof, such credit as to each parcel to be made upon the unpaid installment in inverse numerical order; provided that if as to any parcel there shall be no unpaid installments or, if the unpaid installments are less than the amount of the credit, then such total or surplus amount of credit shall be applied toward the payment of the next City tax levied against such property. If the City shall have been assessed for any portion of the cost of the improvements, then it shall be considered in the same category as the owner of private lands and shall be entitled to its share of any such excess except that any amount due the City, which in case of private lands, would be applied to the payment of City taxes, shall be refunded to the City in cash.