The cost price of a position is for reference only, and it may be calculated inaccurately, particularly in situations where a corporate action or a position transfer takes place，but such errors have no impact upon the account equity. You can modify it by contacting customer service.
Futu uses the diluted cost price, and the calculation formula is:
(total buy amount - total sell amount) of the holding period/ Number of positions. When the total sell amount of the holding period exceeds the total buy amount, the cost price will be negative.
Because the P/L% = (current price - cost price) / cost price.
If the cost price is negative, the P/L% will turn to 0.00%，which means no reference value.