I was of the impression that reading a graph also required understanding of regular writing/reading, but I'm no native speaker, so I'll gladly stand corrected.

I'm not sure what you mean by "one of those little zigzag indicators", do you perhaps mean leap/break in data denoted by the "Squiggle"? I don't think any data below 7m is included in this graph, so, if I understand you correctly, then that wouldn't be a proper use of said squiggle.

[–] Feathercrown 6 points 1 day ago

Yes, I mean an axis break to denote that part of the axis has been omitted. Using it to show a gap between 0 and the lowest included data in the dataset is very common and is a proper use even according to your own source:

A zigzag on the line of the x- or y-axis in a line or a bar graph indicating that the data being displayed does not include all of the values that exist on the number line being used

Beginning the Y axis at 0 and using an axis break to go from there to 7 million allows you to see the same amount of detail as you can in the OP, while visually signalling to the reader that the scale on that axis does not show a full 0 to 10 million range. This increases the chance that they'll read the graph correctly. You can justifiably blame someone for reading it wrong, but the point of a graph is to communicate, so minimizing the chance for misinterpretation is a good idea.