You can set the pre-open and post-market prices to calculate the market value and profit and loss in these two time periods (used/not used), but based on risk control reasons, and also refer to the industry’s handling methods, in the pre-open and post-market stages (the table below Green part), Futu will use the pre-open/post-market price to calculate margin, so this setting is only used to show the market value and profit and loss of your positions.