The numbers that you dial into the devices are address numbers. They're shortcut addresses. Instead of saying "Pull Station, 2nd Floor, North Stair" you dial in the 2 digit number. It's much easier for the electronics to use a 2 digit number instead of the long description; the short number takes a lot less time to send than the long description.
Each device is going to have its own number. Each smoke detector is going to have a different number from every other smoke detector, and will also have a different number from each pull station, each heat detector, each waterflow switch, each tamper switch.
The reason for the different numbers is so the panel won't get confused. For instance, if a smoke detector had the number 37, and a pull station also had the number 37, the panel would think there's only one device, and send the firefighters to the wrong location.