Experiment don't want to start because of screen size

OS: macOS Big Sur 11.0.1
PsychoPy version: 2020.2.10

When I want to start my experiment, this text is appearing in the Runner Box:

WARNING: User requested fullscreen with size [1024 768], but screen is actually [1440,900]. Using actual size

I already changed the size of the screen in the monitor Center, but it didn’t worked.

Thanks you for help.

What the message is essentially saying is that you’ve told it (in the Monito Center) that your monitor resolution is [1024, 768], but your monitor resolution is actually [1440,900]. PsychoPy can’t change your monitor resolution, so is forced to use the actual resolution.

To change your monitor resolution, you’ll need to do so on your computer itself. Here is a guide for Mac: