nnml-generate-nov-databases - What Did It Do?

[khj]

[ Ubuntu 10.04;  GNU Emacs 23.1.1;  Gnus v5.13 ]

Recently, I noticed that one of my groups began asking me upon entry, "How many 
articles from <newgroup>?"  Though I lived with that for sometime (by just 
hitting <enter>), I eventually decided to try and fix it.

The first thing I did was to select all articles in the group and "move" them 
(gnus-summary-move-article) back into the same group.  Hoping they'd be 
renumbered correctly.  That didn't work.

Then, thinking that I'd used 'nnml-generate-nov-databases' in the past to fix 
similar "problems" , I -- with some unease -- went ahead and executed it: M-x 
nnml-generate-nov-databases.

Well, besides not fixing the target "problem", the last approach seems to have 
done other than what I expected it to do.  Though things are working OK 
(sending/receiving mail), Gnus is much slower to start and a new (what appears 
to be) group shows up in my main buffer called "Archive.to" with 200,471 
articles!  Now ~/M/Archive/to *is* the directory in which I "archive" sent 
mail.  But I don't understand why "Archive.to" showed up in the "*Group*" 
buffer and the slower startup time ...

So, I am turning to the experts with questions:

  (1)  What is that "group"?  
       Why is it there? 
       Can I safely get rid of it?
       If so, how?

  (2)  What is the correct way to eliminate that "How many articles ..."
       prompt?

Thanks for your ideas/comments!

-Kenneth