Screen resolution won't change

[not a gamer]

I'm playing Giant Machines via Steam Link on an Apple TV. The program running Steam is a Windows 10 PC. When I have the game open, I attempt to go into options to change the screen resolution. It starts off on 1024x768. I am able to select a different resolution like 1920x1080, click apply and save. It does something because the screen looks less blurry after that, but it still does not fill the screen as it should. It is still like a box in the middle of the screen. Is this some kind of a bug? I do not have this problem with other games like: Farming Simulator, Lego Worlds, Mud Runner...etc.