Today, just for kicks, I have been doing my own speed tests, and come to the conclusion that you can not trust the results the speed testing sites reveal at end of test.
I ran 4 different speed tests in succession from same device, on same network. I get 4 very different results, the Zen speedtest.net says 400Mbs, I know my line is faster than that, as I can download a Windows 11 ISO from Microsoft website quicker than 400Mbs. speed.cloudflare.com says 700Mbs (if I was going to trust one it would be this one, it 'feels' right), fast.com says 1.1Gbs, and BTW speedtest says 1846.43Mbs, ie twice the physical speed of my connection! All show different speeds and different ping times, so its all nonsense, and I now don't trust the figures they report after my little experiment.