You do not need a specific version numbers to watch, just to keep the greatest mathematical.
Google version number: e.g. 5.0.375.70
The first and second number (5.0) the major version number, the third (.375) the current/sub version code, and the fourth (.70) the small update number.
The launcher (Chrome.exe) dont use old folder. Google chrome installer, updater does not delete the old directories for reasons of safety, in case someone wants to return back to the previous version. But this brings all the previous version. Each version 100Mb (the installer backup and runtime files), only manually delete the old unused runtime folders.