If you've set your 2x2 video wall, but the image seems to run off the screen, or not fit evenly on all sides, you will need to turn on 'Fit to Screen' on your TV. 

The 'Fit to Screen' setting can be found under picture size settings on most TVs. You might see that this setting is set to 'Auto', but it will need to be set to 'On' to take effect.