Day Trader’s Aftermarket Lounge 4 Aug 2020, page-75

Orders are cued from 7am AEST by price and time. That is a higher price will trade prior to a lower price. A trade placed at a price will trade before a second trade placed at that price. The bids then take out the sell stack, so depending on its depth you may well bid high to ensure you get a priority buy on stock below your target price. You may pay less but cannot pay more than your bid. So you need to consider how much you are willing to bid to secure stock at the open. There's great info and tutorials on the ASX website.

Trading at the open is tricky and it is easy to over pay. I only do it if I have a clear target - a NASDAQ lead is a good way of having that clarity, although some stocks are led by the ASX.

In your ATHE example you are a decimal point out. At current prices US$3.50, equivalent is about A$0.072 on the ASX. Should be a good result for those who held overnight. May continue on if the FDA approval is perceived as likely, their lead drug is showing safe and some effects to combat Parkinson's (see the Ann 01/07/2020 and yesterday).

There is further excitement around ATH / last time I did that nasdaq equivalent math after a rise (01/07/20) the equivalent was $0.036 and it ran 2000% the next day!(but retreated to the equivalent later, burning a lot of punters).