In addition to 4,751.5 acres of non-Indian land included within the two irrigation Districts dealt with in subpart A, there are 3,237.6 acres of land, more or less, in non-Indian ownership under private ditches, covered by repayment contracts executed pursuant to the act of June 28, 1946 (60 Stat. 333-338), obligating such owners to pay their proper share of such construction costs. The total per acre charge against all such lands is $26.38. This amounts to an annual per acre rate of $0.6595. For the purposes of this notice the annual per acre rate is hereby fixed at $0.66. This annual rate of assessment will continue for a 40-year period within which the total amount of construction cost of $210,726 is to be repaid without interest. The amount of each annual installment chargeable against the lands covered by each of the several contracts with individual landowners whose lands are served under private ditches, shall be determined by multiplying the total acreage, under each contract entitled to Willow Creek storage rights, either directly or by substitution, by the per acre annual rate. Against the amounts due annually by the individual landowners whose lands are served by private ditches, under this notice there shall be allowed any credits due under section 6 of the act of June 28, 1946. Credits due on behalf of any land shall be reflected in any statement submitted to the landowners.