Ann: Significant growth in medical cannabis prescriptions, page-25

Yes I think you have the gist of it, what 'gap' means is that there is a gap in the price chart, a stock price might 'jump' up or down at the market open leaving a gap in the chart for reasons that you posted. For some reason charts hate gaps and VERY often a price will retreat (or go up) in order to 'close the gap' before continuing up (or down).

Check out the BDA chart in this thread and notice the 2 big gaps. https://hotcopper.com.au/threads/chart.4873969/ It's possible they will be both be closed (at some point) but I would expect at least the first one to close. Occasionally a chart will form a gap that never gets closed but IME that is the exception rather than the norm.