I tell you clearly that this topic is wrong and the examples in the book are also wrong.
First of all, the futures contract of March 1 is 3,400 points, not 3,324 points, so shorting a single futures from March 1 to September 100, the loss is 100 points, not100 points.
Your simple understanding is that short selling means losing money when it goes up, and long selling means accompanying money when it goes down. Because he shorted at 3400 points, the delivery date was 3500 points, and he lost 100 points, so it was negative. As for the pricing method of delivery settlement price mentioned by several other guys, I won't discuss it. Consider the 3500 point mentioned in the title as the settlement price.
The person who had this problem was really kicked in the head by a donkey, moron! ! ! There are many mistakes in this book, which is a headache.