When filing documents or when creating a Time entry, when selecting the Job this displays as default all the jobs for the client that has been selected in the filing details.
If required for your practice, an FYI Admin can set your Practice Settings so that when selecting a job, this shows all the jobs that exist for any client within the Client Group, not just for the selected client. This is done by removing the green tick for Show jobs by client to set it to "Off".
Refer to Show jobs by client in Managing Practice Settings.