Chuancang means that after the trading account is forced to close its position by the platform, the account balance becomes negative due to various reasons such as sharp fluctuations in market prices, that is, investors owe money to the platform. Since the money owed by investors to the platform is actually the money owed by the platform to the liquidity provider, investors are obliged to make up the negative value of the account after the short position occurs, otherwise they may face the risk of being sued by the platform.