You're in the most heavily shaded region. Some of the areas reach most of the way around the world, so they look like a lighter circle that you're actually outside, some are smaller and look darker which you're inside, some are about halfway and look like a sine wave, but they're all really circles. (Damn you, Mercator!)
I assume each circle has a radius proportional to the rtt, thus the area in which the circles overlap is roughly where you should be. The limited amount of servers + wide range of rtt gives a massive margin of errors, but this is probably easily improvable through some extra servers and some kind of knn-ish analysis.
Well in my case somehow javascript places Singapore circles center to middle of Indian ocean close to Antarctica. San Francisco and Bangalore are in South America.
That's not an inclusive circle, it means anything within the circle is _not_ reachable within the RTT reach of ie. Bangalore or Singapore.
The best circle is about 1500 miles off from my actual location. The most overlapped area isn't even in the right continent, let alone country. I think massive margin of error is a bit of an understatement.