From a scatter plot, I can see x axis, which is population_proper, ranges from 0.0 to 1e7. Can anyone what that numbers mean?

Perhaps the following message from the lesson FAQ will help-

Does that clear up the confusing notation?

Thereâ€™s a wikipedia page which covers it and a few other notation forms youâ€™ll be likely to come across:

I know what 1e7 means. I am curious why the range stands between 0 and 1e7.

It doesnâ€™t, or at least not quite. You can get the exact limits of the graph by testing the `.get_xlim()`

property of the axis object (apologies if that doesnâ€™t mean much right now). A quick test seems to suggest the actual axis limits are roughly

-39,000 to 8,963,000 (this may be altered by the changes I have made since these are auto-fitted limits by seaborn/matplotlib).

But even by eye the limits are roughly 0 (or just below) to about 9 million. So it doesnâ€™t quite reach 1e7 (10 million).

The 1e7 in that image should be offset slightly below the axis ticks (0.0, 0.2, 0.4 etc.). It means that these numbers are the result of dividing the real numbers by 1e7 (so to get the real numbers multiply by 1e7). The graph itself never reaches 1e7 as a limit (more like 9 million or so, which would be 0.9 with the given notation).