With respect to support orders that require payment of support to commence on a day other than the first day of a month, the child support enforcement agency, for purposes of monthly administration, shall compute a pro rata amount due under the order for the first month of the period of payment, in the following manner:
(A) Determine an annual amount under section 3121.52 of the Revised Code;
(B) Divide the annual amount by one of the following to obtain the daily rate:
(1) If payment of support is required to commence in a leap year, three hundred sixty-six;
(2) If payment of support is required to commence in a year that is not a leap year, three hundred sixty-five.
(C) Multiply the daily rate by the number of days the order is in effect in the first month, including the date payment of support is required to commence and the last day of the first month.