By default, all documents in a given context are subject to the same rights. However, the need may arise for exceptions to be made for specific documents. For example, it might be necessary to allow an auditor access to a specific secret merger document, but not to all secret merger documents.
To support such exceptions, every sealed document has an item code.
In most cases, item codes are allocated and managed automatically. In rare cases, users may be authorized to allocate and change item codes manually. This enables a user to, for example, create several different documents all with the same item code, enabling the documents to be handled as a unit for the allocation of rights.
Item codes are changed or retained depending on your rights. If you have the Seal right, then when you save (or save as) any edits to a document, a new item code will be created for that document. If you have the Reseal right, then every time you save the document, the same item code will be used.