Risk warning: Many stock investors often don't understand this problem when they do futures trading for the first time. After buying a stock, as long as you don't sell it, the profit and loss are on the books and can be ignored. However, futures are different. They are all margin transactions, and the profit and loss are settled every day. Book profits can be withdrawn, but book losses must be covered by margin. The basis of calculating profit and loss is the daily settlement price, so the cost price of the remaining positions becomes the settlement price of the day after profit and loss settlement.