Buys and sells are transacted at open price (or the 10.11am price) up until 10.30am as the prices are 10 minutes delayed.
Buys and sells placed after 10.31 will be transacted at 4.33pm taking the close price.
We need to take into account that the auction open doesn't conclude until 10.10am, and know that our own prices imported from the ASX are 20 minutes delayed.
