Borderless Window Mode Only Shows 1/4 of screen

I started the game, and switched to borderless window mode and now it only shows the top left 1/4 of the entire game. To be clear, it fills the entire screen, but all I see is the top left quarter of the game. It's as if I've zoomed in on the top left quarter. I'm playing on a 4k tv. The top left doesn't go far enough to click on the settings to change it, so what should I do? I've already restarted comp, and repaired the game files.