How to determine sale value in case of Export of goods on consignment (FBA shipment) to Amazon USa

I am a seller based in India sending goods to amazon USA for sale. Since the goods are going on consignment basis to their FBA warehouse in USA, and I realise the payment from Amazon when actually sale happens to individual customers through Amazon USA portal, I am unable to determine the value at which I should create invoice, at the time of shipping. The sale price fluctuates due to discounts given later on to boost sales. Also amazon charges commision and local shipping fee, resulting in a lower remittance as compared to the actual selling price of my product in USA. My questions are - 1. At what price should I make the export shipment? Gross selling price at which it is sold to customer in USA or a net value (net of estimated amazon USA expenses). If I declare sale value on gross Basis, I will always realise a lesser amount from Amazon USA and hence it seems incorrect. 2. If I declare sale at net value, it’s ideally not a correct sales value and also how do I treat mismatch in estimate sale value and actual remittance received.