definiens: shall mean the gross amount inv oiced by Purchaser or its Affiliates for Product sa les, less : ( i ) reasonable and customary cash discounts c onsistent with the Seller ’s past practices, ( ii ) cu stomary rebates and Chargebacks, consistent with the Seller ’s past practices and ( iii ) sales credits, refunds, returns and allowances accrued by Purchaser in accordance with GAAP . Such amounts shall be determined from books a nd records maintained by Purchaser in accordance with GAAP, consistently applied . To the extent that any accrual contemplated by the foregoing clause ( iii ) is subse quently adjusted in accordance with GAAP, Purchaser shall notify Seller thereof in writing and the Earnout ow ing hereunder in respect of the Product Net Sales corresponding to such accrued amounts shall be adju sted accordingly and the next subsequent Earnout pa yment hereunder shall be increased or decreased according ly