The naming is a bit confusing but it's not too hard to get a handle on it:
- Acrobat DC has two tracks: Classic and Continuous (they are both DC products).
- Tracks names don't have much to do with the licensing method, though Continuous tracks usually uses named user licensing and the Class tracks usually uses serial numbers. Ultimately, the licensing program you bought into determines this, and the admin guide page you reference is up to date.
- Serial numbers are for one track or the other, so if you have a serial, install the correct track.
I'm not a licensing whiz, but I expect you buy a volume license for the number of seats you need to else buy more licenses.
HTH