[Koha] Biblioitems table

We just imported our collection into our new Koha installation. It went really smoothly. Based on the schema, though, I was expecting to find a sortable call number in biblioitems.cn_sort. Since we don't circulate any materials, I didn't create any items. Is there something I needed to set or map to populate this field when I redo the import? Or, should I just add item information? Thanks, Lezlie Questia