Not getting no where near the speed I pay for.

As the title says. I pay for 2000mb down and 350mb up. I run the modem Xfinity uses. I am hardwired to the 2500mb port and I have a network card that can handle up to 2500mb. But the fastest speeds I can get are around 520-ish mb down. The up runs just fine. I recently had techs here to fix a bad install a subcontractor had done. They showed me the speeds coming into the modem was 2200ish. But I can't get my computer to pull those numbers at all.