Have you had to reinstall an R710 with an older version of Microsoft Windows recently and find that your R710 display will only use the default Microsoft version? The R710 has the Matrox display integrated video and even the SUU will not detect it at first.
NOTE Disclaimer: This is not an official Dell Supported way of doing things, proceed at your own risk!
Okay, now with that out of the way …
You’ll want to go to the Dell support site and download, then install, this driver: https://www.dell.com/support/home/us/en/04/drivers/driversdetails?driverid=hrvnd
Hope that helps and you can now see the full screen instead of what you are probably seeing on your current R710 Display 😉