10 hexes on the travel map would be 100km. So it's not that.
I agree though, there are many occasions throughout the rules where the word "hex" is used very simply and several occasions where this is potentially very confusing.
As for the distances, it really depends a lot on a ton of factors. Cloudy night? Ambient light? Are your eyes adjusted to night vision? Even full-moon factors can vary enormously. You can sometimes see surprisingly far, but the ability to focus or make out details is almost non-existent. The eye uses entirely different physiology to see at night as compared to day (and the techniques you need to use to get good at it are also therefore completely different!) Real nerd shit.
I'm running a game in Foundry, which fortunately provides for "Vision" and "Dim Vision" -- allowing me the opportunity to simply house rule this that within bright vision you can see pretty much fine, but within the range of dim vision (2-3x bright vision) you can only make out vague details like "That's a peron, that's a truck, that's a tank," and not always correctly. This will fuel my crazed desire for traumatizing blue-on-blue scenarios.