ajedge, the following may allow you to understand the opening...

ajedge, the following may allow you to understand the opening and closing auction
https://www.rivkin.com.au/blog/shar...e-asx-opening-and-closing-auctions-24222.aspx

The very high buys are matched against the lowest sells, this carries on until such time as the buyer is not paying more than his offer and the seller is not receiving less than his sell price. This point is then set as the opening or closing price which all those buyers and sellers buy or sell their shares at. It is an area whereby a bot due to speed can influence the opening or closing price with the buy or sell of 1 single share.