After the first batch of payment is fully deducted, it means that all the payment paid when purchasing a batch of goods for the first time has been used to pay the cost, price, tax and transportation expenses of selling the batch of goods, and the balance of the payment has been liquidated and no longer exists. "First purchase money" refers to the money paid for the purchase of goods in the first transaction. "Deduction" refers to the expenses incurred in selling this batch of goods with the payment, mainly including cost, price, tax and transportation expenses. "Full deduction" means that the first payment has been used to pay all the expenses of selling this batch of goods, and there is no balance.