It uses https://freegeoip.net/ but I have no reason to think that that's any more accurate on average than any of the other services that do the same thing. Maybe someone at your ISP is buddies with them and has given them more accurate information. *shrug*

>(It was also labeled something like "project", which is what led me to
>interpret it as the system's attempt at indicating where it
>was.)

Thanks for pointing this out; I've revised the legend and hopefully it will be less confusing now.