If the futures are at 3500 points at a certain moment, and you think the futures can reach 4000 points at maturity, you should immediately place an order and buy at 3500 points (that is, you can buy at 3500 points). If the purchase is successful, you can use 4000 points to buy goods at the agreed price of 3500 points, and sell them at the market price of 4000 points (selling positions), and you can earn 4000-3500 = 500 points.

The main futures contracts are very active. If you really buy goods at 4000 points (in fact, the entrusted price exceeds the limit of the daily limit, which is invalid), you can also trade at 3500 points without raising the price to 4000 points.