Hi Marcel,
When you Add a Plane (or any Mesh), the first time it comes in at a size of 2 meters. When you change the parameters in the ‘Adjust Last Operation’ panel (bottom left, or F9), the next time it will Add the Mesh with the parameters you last used. (Until you close Blender, then it ‘resets’ to the default.)
I have no idea, why the video reacts to Spacebar, when you’re typing in the text box…
