IP info in Anyonymous Test

I'm not sure if this is the right forum or not, but here goes... I took the Anonymous Test and it showed my external IP address correctly, but also claimed it could see my internal IP address. However, the internal IP address it listed was actually my router's IP address, not my computer's static internal IP address, as shown in Network Configuration. I wonder if you could explain more about this. Does your test actually mean the Router's IP address when it says "Internal IP address", or does the test result mean that my router's hardware firewall has stopped your test getting at my internal IP address?