To obtain an announcement number authorized by the State Intellectual Property Office, you must first apply for a document number
The document number is the only basis for obtaining a patent specification.
If uniqueness is the characteristic of the application number, then the characteristic of the document number is multiplicity.
Once an application is accepted, it can be published once or multiple times according to the review system and approval procedures, resulting in an application having only one application number but multiple document numbers.
One-time announcement: generally the result of implementation of registration system and complete review system.
Usually the issued patent specification or published specification is published.
The document number at this time is the patent number or announcement number.