The master is the volume. Generally, two transactions are counted at a time, which is the transaction volume within a certain period of time;

Location is cumulative. Since the listing of this contract, more than half of all open contracts are single and half are empty. If both buyers and sellers open positions, positions will increase by 2, and transactions will increase by 2. One opening position and one closing position clinched a deal, and the amount of positions remained unchanged, and the transaction increased by 2; If both buyers and sellers close their positions, the positions will decrease by 2 and the transaction will increase by 2.