Different speeds displayed from different speed tests

Hey guys, I'm one of those customers that have that "rare 30MBPS stuck internet connection" glitch on my router that is "supposedly unfixable," and I'm here to follow up.

 

I have been testing my internet speed on google from all of this (searching up "speed test on google), and the speeds are capped at 30-40 fps, however when I test it on the xfinity website (http://speedtest.xfinity.com/), the speeds are very much similar to my purchased maximum internet speed. This is very odd as I feel like my internet connection is very slow (30-40mbps). This was through wifi and ethernet; speeds don't differ on google speed test or xfinity speed test.

 

If anyone knows anything about this, please share it with me so I can possibly fix this problem once and for all.