I reckon they were slowly accumulating majority that was on offer today. The Auction was just to see if could draw out few more 100,000+ dumpers like there has been in recent auctions.
Auction was only 615,000 so to have a left over 4.47M order means they quite likely cleaned up a fair bit of that.
A bit reminiscent of the run from low 40's back up to 53 few months back when a buyer wanted to enter with a sizeable position.
Screenshot just post auction close.