Changing logo size

Hi. I’m having difficulty changing the logo size. I uploaded a logo with an approx soze of 200 x 50 pixels.

I then changed logo width and height to 0 and then the logo became very large. I then changed to 200 x 50 whereupon the logo appeared to be the default size. When I tried to make bigger by, again, changing increasing the settings there was no effect. (I am resetting my browser cache—so it’s not that.)

How exactly is the width and height settings supposed to work? You show units as “Append px or %”. I’m unclear what that means.

Is there automatic scaling going on? Can I make my logo proportionate to the Headline and Description text? (That is, about the same size.)

Thank you.