Each row says what is behind its code before you follow it. Article — the entry is written and has its own page. Brief — no page of its own yet; the link leads to whatever holds it. Register row — the code exists and the entry is not written. The register is wider than the library of written entries, and always will be; this line is here so the interface does not pass one off as the other.
No entry in this Part carries a page yet: each holds a code and a row and nothing more. That is the honest state of the Part, and a code without an article is still a permanent address — this page answers to it. Counts and order are read from register v60.25 at build time; they are not maintained here.