First, note that Subversion has no concept of projects. The repository just stores a versioned directory tree — you may consider certain sub-trees to be projects, but Subversion doesn't treat them differently from any other sub-tree. Thus, the interpretation of what constitutes a project in the repository is left entirely up to the users. (This is similar to how branches and tags are conventions built on top of copies, instead of being basic concepts built into Subversion itself.)

Each time you commit a change, the repository stores a new revision of that overall repository tree, and labels the new tree with a new revision number. Of course, most of the tree is the same as the revision before, except for the parts you changed.

The new revision number is a sequential label that applies to the entire new tree, not just to the files and directories you touched in that revision. However, colloquially, a revision number is used to refer to the change committed in that revision; for example, "the change in r588" ("r588" is shorthand for "revision 588") really means "the difference between repository trees 587 and 588", or put another way, "the change made to tree 587 to produce tree 588".

Thus, the advancing revision number marks the progress of the repository as a whole; you generally can't gauge the progress of a particular project within the repository by watching the revision number. Also, the revision number should not be used as the publicly-visible release number of a particular project in the repository. For that, you should devise some other mechanism of distinguishing releases, such as using