As commented @ https://github.com/kordan/moodle-mod_surveypro/pull/361 (CONTRIB-6952), each time we branch, it's required to bump all the master versions of the plugin to current date. And since that moment:

• stables only get +1 increments, keeping the old YYYMMDD unmodified.
• master always increments to current date.

That's needed to guarantee, basically, that all the master versions will be, always > than the stable ones, and no "downgrade" situations will happen.

You can find more information about this @ https://docs.moodle.org/dev/Moodle_versions and linked pages.

CIao