An empty order means that the player's buying and selling direction is to buy down, and he thinks that the price will fall for a while. The short position is that his margin is not enough to support the current price. Simply put, the margin is gone, but the price is still falling, so your order is forcibly closed by the system. Stock index futures fluctuate rapidly from time to time, so they will basically watch the market. If you have a lot of margin, you don't have to worry about short positions! Of course, there are also profit-taking and short positions.