What’s the monitor that you have? 23L11-H-AN
Is this it? https://ktc-tvs.en.made-in-china.com/product/iblQwIkECqYy/China-23-Inch-LED-TV-23L11-.html
The issue you are seeing is physically with the display resolution. The reason a screenshot won’t show that is because it takes a picture of what the computer thinks it’s displaying not what is physically being displayed on the monitor.
I have seen it sometimes on TV’s and such where it overscans and I think that is what you are seeing.
On the physical TV/Monitor can you change any “scan” settings? Sometimes it’s called “Just Scan” or “Overscan”
Article about it: https://www.howtogeek.com/252193/hdtv-overscan-what-it-is-and-why-you-should-probably-turn-it-off/