Where to look for the source of the set margin values?

I have 3 nested elements:

The last one (Intro) has margin values coming from somewhere else (the default), but I have no idea where exactly from, because the two higher layers do not have these settings.

Where to look for the source of these values?

I think something is stored somewhere in the theme styles

Found it!
I don’t know if this is normal behavior or I don’t understand something. The margin values I showed in the previous screenshot depend directly on the width value set in the element:

But they also depend on the current width of the browser window, when I expand it the values increase:

And one last thought. These margin values don’t change in real time, when expanding the window, and they don’t set right away when you first enter the width value, but they appear after you change the active element to another (focus) and then return. Therefore, I could not find this dependency.

Is this the way it should be? Is this the correct behavior? Because for me this is a serious problem.