My serial number has only 9 digits. Now what?

My serial number has only 9 digits. Now what?

myAir supports all AirSenseTM 10 or AirCurveTM 10 machines with built-in wireless technology, where a supported wireless network is available. These machines all contain an 11-digit serial number and a 3-digit device number on the back of the machine.

Where can I find the Serial Number and Device Number of the machine?