Some Chocolatey packages get updated between official program releases and have their own version number. Examples:
3.3.11.20170322 (official release notes) 1.1.2.20161210, 1.1.2.20160811, 1.1.2.20160317, 1.1.2.20140225 (WinDirStat homepage)A package in a package management system usually contains more than just the bare minimum as it is part of some kind of eco system. Usually there is some kind of maintainer for the package and he decides what to do with it.
In your case you use links on the left side of the site in order to access additional information about the packages and contact the maintainer. If you're unsure what he's doing or there is no way to get any details, it's your best bet to contact the maintainer or stop using the package. For qBittorent you can see that chocolaty themselves are apparently the maintainer and using the link Package Source on the left, your're able to view the git repository for that particular package.
If you view the history for the repository you will see every commit that influenced it's contents and by clicking an actual version (e.g. the one you mentioned) you will get details on what actually changed. For binary files you wouldn't see much but for text based files you will. In this case there was a rather arbitrary increase while the automatic Audacity package actually changed.
In case of WinDirStat the maintainer is a third party but again there is a repository available and you would be able to view changes the same way. In your case an example would be WinDirStat 1.1.2.20161210. That commit looks primarily like a license update.
