I have the Gigabit Conneciton Plan, but can't come close to 940/880Mbps

Hello - I have the following:

• Verizon FIOS Gigabit Connection (up to 940/880Mbps)
• Verizon FIOS Quantum Gateway AC1750
• Desktop computer wired to the router (no WiFi for this particular connection)
• Cable run of under 50 feet of CAT6 cable from router to computer
• My desktop does have a 10/100/1000 Mbit Ethernet card.

When I run Google Speed test I typically get speeds of between 400-600Mbps download and 100Mbps upload.  

Is there anything I can do to get it closer to the stated limits of the plan?  

Thank you.