The case has been solved. The final profit of this friend's short position is 1000U.

When the volatility is large, our strategy is to eat both long and short positions. He also eats both ends. The long and short positions are the same size. The cumulative profit of the two strategies on Friday is 2000U.

Today's volatility is not interesting. The volatility tomorrow, Monday, will be very violent. Basically, both long and short positions will explode. You must enter the market at a very advantageous point to make a profit. If your point is not good, you can only find it by position. #BTC