I could be wrong here but as I understood it and based on the...

I could be wrong here but as I understood it and based on the shared link, a gap is created when there is a sharp drop or a sharp increase in price without trades going through, at any given time.

The gap in discussion here is likely when a large parcel, or a number of large parcels, were set to trigger a stop loss at a certain price, creating a sharp decline in the share price at the aforementioned gap price indicated by @$tock1

The gap was picked up by new buyers, filling the gap, forming a new bottom.

Who knows, my research is a lot better than my charting, thought I'd give it a go and try and explain as to how I understand it.

Someone here can confirm, though.