For example, you buy 500 lots first, then sell 300 lots, buy 400 lots and then sell 500 lots. At this time, you bought a total of 900 lots, and you can buy up to 300 lots that day. After that, you can only close the position and not open the position. However, open positions (short positions) can be sold, and the cumulative quantity shall not exceed 1200 lots.

The full name of stock index futures is stock price index futures, which can also be called stock index futures and futures index. It refers to the standardized futures contract with the stock index as the subject matter. The two sides agreed that on a specific date in the future, they can buy and sell the underlying index according to the size of the stock index determined in advance. As a type of futures trading, stock index futures trading has basically the same characteristics and processes as ordinary commodity futures trading.

The essence of futures is to sign long-term contracts with others to buy and sell goods (or stock indexes, foreign exchange, interest rates) in order to achieve the purpose of maintaining value or making money.

If you think the futures price will go up, go long (buy and open positions), go up (sell) and close positions, and earn: price difference = close positions-open positions.

If you think the futures price will fall, short (sell the position), fall (buy) and close the position, and earn: price difference = opening price-closing price.