Ethernet wired link could be operating at 10,100, or 1000 Mbps mode depending on equipment and cable. If your Fingbox tests are consistently low compared to other tests (ideally also using mLabs as already suggested), try using a different Ethernet cable or different physical port on your router.

For most consistent results, I suggest remove all WiFi and only connect by Ethernet wire into your router or modem. Likely the highest results you are seeing when testing in browser do represent what your network is capable of achieving.

When testing in a browser to Ookla or ISP, the Fingbox is not involved. Fingbox can run an internet speed test on a schedule and on demand, the Fing App on a smartphone can run a speed test direct from phone to the internet or a WiFi speed test between the phone and the local Fingbox or trigger the Fingbox to start a test, the Fing client on a Mac or PC apparently can run a speed test too but unclear if it's triggering the Fingbox or going direct to the internet based on the image shared (I don't use Mac Client).so there are a lot of tests available and we need to be clear which is being used while troubleshooting.

Internet speed test spectrum ookla