Paul, because it's not labeled pin 14. It's labeled A0. The Arduino also knows those pins as A0-A5. Then to top it off, without initiating the variable, run the same sketch above. but this time have the serial port (user input) write the variable. if you do that, what is reported back is 0-5. I will have a sketch for you to try tomorrow. its late here.
I am not trying to be a pain or anything guys, but this isn't right the way it's reporting. Does it REALLY REALLY matter? NO. I can teach the kids however it is, but when you are trying to teach consistency, accuracy and all those things that are hard for kids to completely grasp, this doesn't help. It reports pin 14 one way you do it, then it reports pin 0 the other way. Yet with digital pins, they report perfectly. Why not come here on this forum and ask for help making a bit of code that makes everything consistent?