What is the difference between a package number and a device number?

A device has a number to identify its device type with the specific hardware and software. 

Example: 2014.8081 Exstreamer Store&Play 8 GB

A package is a combination of the device, the power supply (if applicable), the cables and connectors (if applicable) and the packaging.

Example: 2014.9158 Exstreamer Store&Play 8 GB EU Package