I did the division on your numbers also (seems to be 1 to 1.9). I wondered if it was somehow km vs. nautical mile ratio. Or perhaps something weird with widescreen aspect ratio (16:9 or 16:10). But the latter ratios are less than 1.9.
Nope on the middle- of-the-ruler idea, in my case both maps were measured end to end, 720 km give or take a few km. (because of inaccurate placement of the ends at lower map-zoom)
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