Hello,
Actually it doe snot do anything. It was left for historical reason but will be removed in the examples of configuration files in the next releases.
For information, internally, we have now moved to version numbers in relation to the SVN source control system -- which are much more precise as to what version it is, although we have kept the historical numbering (i.e. v7p0r1) for the names of our tags for public release.
So only the tags are named this way -- you can rename it the way you wish locally.
Finally, v7p0 is the principal version number (from a public release view point) and the subsequent releases (-r0, r1, ...) are bug fixes for that same version.
Hope this helps,
Sébastien.