Because China's "Securities Exchange Law" stipulates that stocks cannot be sold short, and arbitrage trading will only occur when the stock index futures price is higher than the spot price. Arbitrage traders sell stock index futures and buy spot. For arbitrageurs who still hold the spot on the futures maturity date, they need to clear their positions according to the futures settlement price. If there are more arbitrage traders, the selling pressure will be concentrated at the same time, which will put downward pressure on the index.

As far as futures contracts are concerned, the delivery date refers to the date when the goods must be delivered.