Keep Recordings Unwatched vs Total

It seems that some of my Passes offer to Keep ## Unwatched Recordings while others Keep ## Recordings (watched or not). Why the difference and why can't I select whether it keeps Unwatched or Total recordings?

You can select to keep only the last ## of Unwatched recordings
or the last ## of Unwatched + ## Watched

You can also limit the total ## of recordings on hand so it pauses recording more until you delete some.

Where's the User Manual?