To put it simply, Zune is describing the official numbers describing the version of Windows Phone your device is currently running. For instance, the "about" app in settings tells you your Lumia 710 has the software Windows Phone 7.5, but the numbers 7.10.(8773) Zune tells you is the actual OS Version. (In my case, the numbers that represent WP7.8 is actually, "7.10.8862.144"). To see the numbers, click the "more info" button in settings>about.
Originally Posted by Michael Camaras
Hope that clears up any questions. :)