Ann: Share Purchase Plan to accelerate work programs, page-195

I suppose a sell bid means a wish to sell for nothing less than the sell price and happy to take more if buyers are willing to pay more.
Putting in a lower bid than the other sellers is a way of jumping the seller queue ie. selling your shares sell first knowing that
trading commences at opening price and not your pre market seller price and not at any pre market buyers price
Determining opening market price is a separate process that determines where trading begins.
Trading is about queueing up and waiting your turn. If you don't want to queue up you either pay more or sell for less and
if you know what you're doing then you do it strategically.
The guy who put in the bid to sell at 0.57 hoping to receive 0.60 has to be careful that the buyers don't pull their
orders on him and he ends up losing his stock at 0.57.
I suppose the systems works in a way that tries to be fair to everyone at opening. If you want to get in first then you need
to take a riskier bid.