When I see information about new releases of OS it tells me the package version, Applications level, and platform level. Why do I have so many different numbers and what do they all mean (see below for example).

Software For BlackBerry® Storm 2 (TM) 9550 smartphone

BlackBerry Handheld Software v5.0.0.1612 (Multilanguage)

Package Version:
Consisting of:

* Applications:
* Software Platform:
* File name: 9550AMEA_PBr5.0.0_rel1612_PL4.2.0.427_A5.0.0.983_I nland_Cellular.exe
* File size: 120.86MB