Cover file number consists of the full file number, catalog number, and file number.
Full file number: the number assigned to the filing unit by the archives.
Catalog number: the number of the directory to which the file belongs to the full file, in the same full file is not allowed to duplicate the directory number of the file.
Case file number: the catalog within the case file of the sequential number, in the same case file within the case file is not allowed to duplicate the case file number.
My understanding is that the full file number is given by the archives, the catalog number can also be expressed in terms of the year, and the file number is the running number of the file under that year.
There are multiple catalogs under a full file, multiple case files under a catalog, and multiple documents (i.e., multiple individual files) within a case file. The full file number is assigned to the filing unit by the archives, and for a particular filing unit, multiple catalog numbers can be built under the full file number, and then different case files can be built under the same catalog number (each file has another number, i.e., a case file number). There can be no duplicates within the same affiliation. The three relationships can be compared as follows: 1.1.1, 1.1.2......1.2.1, 1.2.2......1.3.1, 1.3.2......1.4 ......2.1.1...... where the first digit is the "full file number", the second is the "catalog number", and the third is the "case number". The third digit is the "file number".