It was more of how you setup the data, labels and how it handles zooming. Those are default behaviors from the chart.
And yes, the reason for the 7 was because that is what the chart maps it to on that axis. We just provided the label 'Jul' to it. And this means also that if your x-axis has Jul to Dec, then you will see here 1.2, 1.4, etc. instead (because the x-axis now starts with 1, which is our 'Jul' label).
For more advance information on zooming and how to better handle them, here is the link to the charting framework:
You can then further customize the behavior by providing an override via tm1-options-override attribute.