Button placement is strange

in screen.lua:

width = display.viewableContentWidth 

in main file:

  resume = widget.newButton {left = -56, top = btnTop, label = “Resume”, onRelease = resumeAction}

  start = widget.newButton {right = screen.width, top = btnTop, label = “Start”, onRelease = startAction}

Why am I having to use a negative number to put Resume at the left edge of the screen?

Why doesn’t right= do what I think it will on the Start button?

This used to work in Corona 1, some sort of version rot has overtaken me.

Screenshot attached.

Corona Version 2016.2830 (2016.2.18) simulating on MacOS 10.11.6