Router Speed Tests Very Slow

[TotalEnigma]

I just purchased a RAX200 router and when I perform a speed test either in QOS or in the NightHawk phone app, my downloads speeds have trouble getting out of the 400Mbps space. This is very slow compared to the 1200Mbps speeds xFinity is providing me. This isn't really a big deal since the devices attached to the router show speed tests in the normal range, I'm just curious why the router itself is having a hard time getting accurate speed test results.

I am using the latest firmware version on the router (V1.0.3.106_1.0.58) and have factory reset the router several times. I even tried a speed test immediately following a reset with only a single device attached to it, and the results were still the same. I have attached screenshots of speedtests run on the router's QOS screen as well as through the phone app, and I have attached screenshots of speedtests run from Windows 10 desktops attached to the router via wired and wireless connection.

Is this a bug, by design, or something I am doing wrong?

Speed tests run from Wired MacOS computer using Chrome.Speed tests run from Wifi connected Windows 10 PCs using Chrome.

Speed tests run from Wired Windows 10 PCs using Chrome.

Speedtest done from the QOS router screen

Speedtest done from the Nighthawk app

[plemans]

Reason why is the built in speedtest doesn't always pick the best test server to test off. So speeds >500mbps tend to be inaccurate for the built in test server. 

If you're other devices are working properly, getting proper speeds, then I wouldn't worry about it.