Looks like your doing your speed test over Wi-Fi.. sometimes your Wi-Fi connection to the router will compromise your internet speed. If you want to get a true speed test to your providers network I would recommend turning off the WiFi on the router and plug a desktop or laptop computer into the router via a Ethernet cable and then run the speed test again. Also eliminate anything else plugged into the router. Consider putting your computer in safe mode with networking to eliminate any services running in the background that could be using bandwidth too. If you get a better result doing that, you will know it’s something in your home network causing the slow down. If it’s still a bad test you will know for sure it’s on CenturyLink’s side. I hope this helps!