I was just explained this by Kooter today. Essentially all gaps are filled but there are what's called runaway gaps where the stock gaps up on open for example and doesn't retrace. I'd imagine this is on a big move up or on a news day for example.

There's no saying we have to sit 2.25 to close the gap, but if we go sideways for a few days we probably will. A really good NR tomorrow will likely make us completely forget about this gap.

Hope this helps