that was discarded shall be determined based on the amount of such drug that was unused and discarded for each drug on the date of service. (C) Exclusion of units of packaged drugs The total number of units of the billing and payment code of a refundable single-dose container or single-use package drug of a manufacturer furnished during a calendar quarter for purposes of subparagraph (A)(i), and the determination of the estimated total allowed charges for the drug in the quarter for purposes of paragraph (3)(A)(ii), shall not include such units that are packaged into the payment amount for an item or service and are not separately payable. (2) Manufacturer requirement For each calendar quarter beginning on or after July 1, 2021, the manufacturer of a refundable single-dose container or single-use package drug shall, for such drug, provide to the Secretary a refund that is equal to the amount specified in paragraph (3) for such drug for such quarter. (3) Refund amount (A) In general The amount of the refund specified in this paragraph is, with respect to a refundable single-dose container or single-use package drug of a manufacturer assigned to a billing and payment code for a calendar quarter beginning on or after July 1, 2021, an amount equal to the estimated amount (if any) by which— (i) the product of— (I) the total number of units of the billing and payment code for such drug that were discarded during such quarter (as determined under paragraph (1))