Everything on the form requires input except for the Qty, and Price. The information that is required is used for the configurations. If you wish to just put the Shell Hull in just to use as a reference based on a configuration that you got from a friend or from a book, just leave the qty and Price fields blank. Any time you use the "Make Ready to use Ammunition" feature it will subtract what you have in inventory.
Once you are done, click on the Add button to add it to the database.