Because according to the provisions of the HKEx, the rules for the display of the pre-emptive price of shares listed on the HKEx are as follows:
1. Start the bidding stage and close the bidding stage
1.1 if there is a reference equilibrium price, the current price = the reference equilibrium price
1.2 otherwise, it will be equivalent to yesterday's closing price.
2. During consecutive trading periods
2.1 if the securities are traded on a case-by-case basis on the same day
1) if you buy a price > the price of the last transaction, the current price = buy a price
2) if the price of the first price is less than the price of the last transaction, the current price = the first price of the sale
3) other cases the current price = last transaction price-
2.2 if the securities are not traded on a case-by-case basis on the same day
1) if you buy a price > close yesterday, the current price = buy a price
2) if the first price is sold < the price closed yesterday, the current price = the first price
3) other cases the current price = closing price yesterday
For more details, see the HKEx trading mechanism:
http://www.hkex.com.hk/Services/Trading/Securities/Overview/Trading-Mechanism?sc_lang=zh-HK