It’s a Raspberry Pi 2 running the most recent Retro Pie version and it’s composite output
Oh man, have you got an actual CRT?
Anyways yeah, to add to what Floob has said, I believe you need to alter the various overscan values in /boot/config.txt
overscan_left number of pixels to skip on left
overscan_right number of pixels to skip on right
overscan_top number of pixels to skip on top
overscan_bottom number of pixels to skip on bottom
Tweak the values until the video output fits comfortably inside your display.