Many packages built for Ubuntu seem to have a "-0ubuntu1" suffix (or, more generally, -XubuntuY). For example, the version string for a bleeeding-edge package from the nova project looks like:
2011.2~bzr663-0ubuntu1
I understand that 2011.2 is a major version, and bzr663 refers to revision 663 in the bzr repository, but what is the meaning associated with 0ubuntu1?