GreenHopper Classic allows you to create parent-child relationships between versions. For example, you may wish to group your sprints as milestone versions (e.g. "Version 1 m1", "Version 1 m2", etc) under the version for the major release (e.g. "Version 1"). In GreenHopper Classic, you can set up the major version as the "parent" version for the milestone versions. This allows you to view and track all of the issues assigned to the milestone releases under the umbrella of the major release.
All issues under the child version are considered to be a subset of the parent version. These version hierarchies are useful for managing Releases/Sprints/Teams. For example, if you set 'Version 2' to be the master of 'Version 2 milestone 1', then you will be able to view all the issues assigned to 'Version 2 milestone 1' when you view 'Version 2' on the Planning Board.
Which fix version do I see on the cards?
The version displayed in the summaries and cards is the committed version. If you are using a 'Parent' version, the committed version will be the end-child version where your issue resides. Otherwise, it is simply the version where your issue resides.
To set a version as the parent of another version,
Screenshot: A parent and child version in GreenHopper Classic