You're in the wrong area. That's for the switchbar size, which is why your switchbar grew so large. Go to Options under that in the tree view on the left of your second image (Alt-O > Display > Options) and you'll see a dropdown for Editbox Lines. Change the setting there.
Thanks for the screenshot as that helped to show what you were doing. If you had mentioned the switchbar was growing, that also would have pointed us in the right direction.
