Andrea,
I had a chance to test the right alt key today on a desktop keyboard, although Georgy already said it.
A program called "xev" that you can type at the prompt on a window which brings up a square box but if you move the mouse to that little window and type a character, it shows you what the key name is. For left alt, it is Alt_L but right alt has no name. Another anomaly is the left ctrl key which is Ctrl_L and the right ctrl key which is Ctrl_R.
I do not know how to state this in the Manual, but only the Left Alt and Left Ctrl keys should be considered as the correct shortcut keys to use whenever Alt or Ctrl are referenced.