But the panel has 500 by default, as far as I know. Because you have deleted what is contained in the panel, but you don't delete the panel.
And the button (each button) that I add, what is its height, if I have not indicated any?
The thing is that if I want to know later how high is the button, or a label, it tells me zero, when it is not.
Surely I am not doing something right.