Hi,
with a PI400 I am using as monitor a TV,
but under PI OS I am not able to find the correct screen size,
and therefore I do not 'see' correctly the displayed info on the sides.
Thanks for your help

Overscan most likely....

https://raspberrypi.stackexchange.com/q ... on-raspi-4

viewtopic.php?t=370606

(Personally I just gave up & use proper computer monitors.) ;)

you can use wlr-randr to see what resolutions the TV supports.

after bootup, open a terminal and invoke
wlr-randr

outputs suppported resolutions....
might help.

The only people that don't make mistakes are people that don't do anything.

Thanks a lot.
I will try to-morrow.
Good night

you can set the resolution manually:
in /boot/cmdline.txt (add to the front/end of the line, NOT a new line)
-- IMPORTANT NOTE: for Bookworm and Trixie, the file is at /boot/firmware/cmdline.txt !!
video=HDMI-A-1:1024x768@60D
(or whatever resolution you want)

above is 1024 x 768 at 60Hz.

The only people that don't make mistakes are people that don't do anything.