If there is only one empty contract, there is only one contract. You can also double open. Depends on yourself. However, you must close your position after any order is issued. Buying one more order can't close the position. It's not up to you to decide whether to close the position or not. Whether the money is enough depends on you. Otherwise, there will be forced liquidation. This is when you go to the wrong place. If the stock index rises by 400 points, you will also force the liquidation.