you can use the phantom key to assign an advance code you can use in a macro. for example let's say i need to use the zenith record trick to create a long delay that I need in a macro. You don't want to waste a real key on the zenith record because you would never use it outside of the macro. So you can assign it to the phantom key. Same thing for the discrete on and discrete off. If your device supports it, it becomes easier to build your macro if you assing the advanced codes to discrete on or off.