Device name cannot contain a node name.  On the device field, press PF3.

    Meaning:  You included the name of a node in the "Device Name" field.
              BACKUP Manager does not use the  node names or access
              string portions of a specification field.  For more
              information, see "File name format" in the "Concepts ..."
              help topic.

    Action:   Specify only a device in the device name field.