Modem/Router Speeds good, but not at PC?

Was getting some slow speed tests on my wired desktop pc, so I called Xfinity, they sent a tech, and he tested my speeds to and from the modem and router.  Everything tested perfectly (roughly 350 down on a 300 down plan)

But when you test it directly on the PC, it ranges from 50 to 150 down at best.

The tech said something is wrong, but he couldn't figure out what.  Any ideas would be greatly appreciated!

(I am running windows defender as an antivirus/firewall for those that may ask)