MLAT Flight on my Radar: Why?

I guess I am confused about my ability to detect and track MLAT aircraft, especially considering that I don’t think there are the minimal number of stations around me to do such a thing. But having said this, why do I see ‘purple’ MLAT flights on my FlightAware radar maps?

https://www.dropbox.com/s/41i3xsab3tj4sof/mlat.png?dl=0

Also, on my status screen, it says: “Multilateration (MLAT): Supported / Enabled (synchronized with 1 nearby receivers)”

Thanks for any explanation of what I am seeing here.