(1) Long positions, that is, buying first, is equivalent to adding a pile of soil on a flat land, and positions (equivalent to the amount of soil) will increase. Long positions are to sell this pile of soil and raze it to the ground, so that the positions (the number of soil) are reduced.

(2) Empty warehouse, that is, selling first, is equivalent to digging a hole on the flat ground, and the position (equivalent to soil volume) will be reduced. Closing an empty warehouse is to buy a pile of soil to fill the pit and increase the position (soil volume).

Summary: long positions lighten up and short positions increase.

2. Whether closing or opening a position is a transaction, it is a transaction. Therefore, closing positions and opening positions will increase trading volume.

3. Therefore, if the number of flat plates (purchased soil) and the number of flat plates (sold soil) are equal, the position (total amount of soil) will remain unchanged. However, many apartments and empty apartments indicate transactions, which increases the transaction volume.

To sum up: "empty flat" will keep the position unchanged and increase the volume.