Because the month with large transaction volume attracts the capital participation of most institutions and investors, the month with light transaction volume receives less attention, which is the difference between the main contract and other months. Although the main month holds the largest position, it is generally the month with the largest transaction volume, so it is easy to find the opponent's quotation and close the deal, while those months with small transaction volume may sometimes be unable to close the deal because there is no opponent to take over.