Additional stickers

I've seen a ton of examples of interfaces that have een "upgraded" after a period of use with a sticker that provides some extra instructions needed to make the machine do what you expext it to do. After seeing more and more of these enhancements I can't help wondering how the designer come to this design. Diti he not look at the context of use? Was it unclear at that time which digital or analog serie was connected with that button in the interface?