1. "shorting around 890 means selling at this price", not selling, but opening a position at this price means that the price will continue to fall. An empty position means that you can only transfer money at this price. If it goes up, you will lose. So stop loss at 896 means that if the price rises to 896, you must sell your short position immediately to prevent the loss from expanding. This is a stop loss.

2. "The first target 876, near the second target 863; Of course, if you break 879, you can also follow up with empty positions. " It means that if you open a position, you can expect the price to fall to 876 first, and you can continue to hold it below this price. If it falls below 879, you can add positions, but you need a small amount, not too much. At 876, you can consider selling short positions, that is, you can make a profit, or you can wait until around 863, but you have to bear certain risks.

These are the technical terms of futures. For opening and closing positions (the number of positions opened), I suggest you look up the terms of futures trading for a better understanding.

Supplement:

If paper gold can be short, it has the same meaning as futures.

Theoretically, your understanding of KDJ is what you said.