The price difference in this period is indeed to subtract the spot from the futures. As for why we don't use the index basis to use the current difference, we can only say that the straight flush is a market software that prefers stock types. This expression makes it easier to understand the premium. For most people who do stock index futures, many have only experience in stock trading, and there are not many concepts about the basis of commodity futures. Generally speaking, most futures or commodity futures do not use flush software, while domestic futures mainstream generally use quotation software such as Wenhua Finance and Boyi Master.

Generally speaking, regardless of premium or discount, with the reduction of futures contract time, the futures contract price will eventually move closer to the spot price, and how to move closer to the spot will be diverse. As the futures contract has not yet expired, the price trend of futures contracts in different months will also be different, sometimes showing near-strong and far-weak or near-weak and far-strong (recent contracts may refer to near-month contracts or spot and far-month contracts), which is likely to be mixed with some factors, leading to different market expectations.