Thanks, Dan.  

I think I am missing some basic understanding of this parameter then.  In my understanding, if I saw 1000 pageviews total, and 999 of them were internal referrals, then this would indicate 1 user who visited 1000 (999 by clicking on internal links). If I instead saw 1000 pageviews and none of them were internal referrals, it would indicate that nobody clicked on internal links on wikipedia during that time period.  (Obviously visitations start and stop before and after the period in question, but ignoring that overlap).  Is that correct?