If you can see from the market depth for DBS Bank which I took a snap shot after the matching was done at 8:58 am before the market started at 9:00 am, there was lack of buyers and this shows that it was likely the fund managers matched DBS Bank at $15.80 during the open with a gap of $0.10 to the next bid price at $15.70.
So one strategy is to sell stocks like this at the open and buy them back later when the price is lower.