Cleanup ZeroUnit length bug fix

Modify documentation to provide some additional explanation, remove an
unnecessary spec, cleanup some code with better naming.

Change-Id: Ia06b4a501ec09ceaad4160f19d8f607f6dd3d7cc
Reviewed-on: http://gerrit.causes.com/37678
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>