Because, if you are buying, you plan to stop at 50 points. An immediate order is a sale order that is 50 points lower than the current price. If you hold the order in this way, the system will immediately close your order at the current price.
If you want to place an order to stop loss in advance, you can set up a prepayment form yourself, or let the futures company set up a prepayment form in its room. When the stop-loss price is reached, click Send. Some trading systems also support automatic trading (when the stop-loss price is reached, a stop-loss quotation is automatically issued. )。
However, there is no way to guarantee an immediate stop loss in the case of gap opening and price limit.