Buy-up: buy-in corresponds to sell-out, buy-down: sell-in corresponds to buy-out. But I don't know if I can understand the buying time in this way: buying positions, buying futures with the funds in my hand as the beginning of the transaction, selling and closing positions, and turning the futures in my hand into funds as the end of the transaction. At this point, the amount of funds on hand has changed (because the price of futures has changed when buying and selling). When buying falls, sell and open a position: put the futures sold in your hand as the beginning of the transaction, and buy and close the position: take the futures sold before buying the funds in your hand as the end of the transaction. At this time, the amount of futures in your hand is unchanged before and after trading, and the amount of funds in your hand caused by the change of futures price is regarded as profit and loss.