Look at the last paragraph

For stock index futures buying period hedging, when the increase in the spot price of the stock portfolio is less than the increase in the corresponding stock index futures contract price, or the decline in the stock portfolio price is greater than the corresponding When the price of stock index futures falls, that is, when the basis weakens, investors can still obtain a certain amount of basis profit when their profits and losses in the stock market are offset by losses or profits in the stock index futures market. Therefore, buying period hedging becomes a Profitable value preservation. On the contrary, when the increase in the price of the stock portfolio is greater than the increase in the corresponding stock index futures, or the decline in the price of the stock portfolio is less than the decline in the corresponding stock index futures price, that is, when the basis difference is enhanced, investors' profits in the spot market are not enough to make up for their losses in the futures market. The loss in the spot market or the loss in the spot market cannot be adequately compensated by the profit in the futures market. In this case, the purchase period hedging is loss-making hedging, that is, the hedging of loss of basis interest. If the increase or decrease in the price of the stock portfolio is exactly the same as the increase or decrease in the price of the corresponding stock index futures contract, the basis will remain at the original level and will not change. In this case, the profit or loss in the stock market will be the same as the increase or decrease in the stock index futures market. The losses or profits on the market exactly offset each other, which we call complete hedging. What he actually locks in during the buying period is the spot price of the stock at that time.

Similarly, for stock index futures sellers, when the basis weakens, it is a profitable hedging; when the basis strengthens, it is a loss-making hedging; when the basis remains unchanged, it is a loss-making hedging. Fully preserved.