Is for sequential numbering of titles across a given publication context, it is a counterpart to the headings in the document. For example, this sequencing could be as simple as a chapter number and only appear in conjunction with the h1s for that document, or it could be the sequential numbering of every section of a document like is done in Handbook 1 and 2, e.g., 1., 1.1, 1.1.2, 1.1.3 etc,.