The reason why the positive market extension number is negative is the calculation formula of extended income. According to relevant information, the calculation formula of deferred income is: (Expired contract price-newly signed contract price) ÷ Expired contract price, which is an indicator to measure the monthly price difference. It can be seen that when a futures product is in a positive market, the extension income is negative, which will lower the index. On the contrary, when a futures product is in the reverse market, the extension income is positive, which will raise the index.