I don’t know why you’re messing with the resolution? Watch TV with 4K resolution and Peppymeter with 1929x1080 resolution. Run Peppymeter in 1920x1080 resolution and show the photo.
According to your TV photo, your RPi is set to 1920x1080 resolution
I also have a 4K monitor and I watch Peppymeter in 1920x1080 resolution