Buying and opening positions: If you want to make a profit, you must hedge and sell the same futures, that is, the more expensive the futures you hold, the more likely you are to make a profit. Therefore, the calculation of position profit and loss is the price of the day minus yesterday's price. If the price of the day is greater than yesterday's price, it is profit, because if you want to sell on the same day, then the income from buying and selling this futures is the selling price minus the buying price, and the price of the day is the selling price.

Selling and opening positions: If you want to make a profit, hedging and buying are necessary. In this case, the lower the purchase price, the more profitable you are. Therefore, if you calculate the profit and loss of a position, you should also subtract the purchase price from the selling price, that is, if you want to make a profit, you must buy a hedge. In this way, you can calculate the profit or the selling price MINUS the buying price, that is, yesterday's settlement price MINUS today's settlement price. If you want to realize that yesterday's settlement is equivalent to your selling price, the settlement price of the day is equivalent to the buying price, so you should subtract yesterday's.