This setting is for libraries wishing to generate barcodes from within Koha (as opposed to scanning in pre-printed barcodes or manually assigning them). The default behavior makes it so that when you click in the barcode field (952$p in MARC21) it will populate with the automatic barcode you have chosen. If you would rather it only enter an automatic barcode when you click on the plugin (the ... to the right of the field) you can change the plugin used for that field in the framework. Set the plugin for 952$p (if using MARC21 or equivalent field mapped to items.barcode in your local MARC format) for your frameworks to barcode\_manual.pl instead of barcode.pl. Learn more about editing frameworks under the :ref:`MARC Bibliographic Frameworks <marc-bibliographic-frameworks-label>` section of this manual.