The job schedule object, QDFTJOBSCD contains the entries that are set up as schedule for jobs. Jobs can be scheduled by adding a job schedule entry to the job schedule object. You cannot create, delete, rename, or duplicate the job schedule object (QDFTJOBSCD), and you cannot move it to any other library.
The QDFTJOBSCD object is shipped by IBM with public authority of *Change. This is the minimum authority necessary to add, change, hold, release and remove job schedule entries.
Yes, It does mean user has authority to modify the job schedule entries.
It means they have authority to change job scheduler entries; however, they can only change entries that they're authorized to.
For example, if I placed an entry on the scheduler on one of my systems, a normal user wouldn't be able to change that entry just from *CHANGE authority to the scheduler. But if that user also had *JOBCTL special authority, then authority to my job entries are automatically available.
The *CHANGE authority alone would allow users to add their own entries to the scheduler (thereby "changing" the scheduler so that it included a new entry.) It doesn't give authority to someone else's entries without some additional element of authorization.