Since the Goobi days at the end of September there is a new versioning for Goobi workflow. The first release with the new versioning was "Goobi workflow 19.09". The first two figures are for the year, the second for the month in that year.
Should there be a bugfix release, another number will be counted up, e.g. 19.09-1, 19.09-2 etc.