Originally Posted by theducks
I did nothing special:
Alter Tag Browser set to Sort by Popularity, Match Any
(NB My collapse threshold tweak is set to 30)
I now see 2 groups (of 30) of 1-1 popularity
I see the problem, I get all the authors whose name is attached to a Single book. There may be more than 1 Author (with a high count, too) on that book
I think we are talking about different things,
When I sort by popularity and expand the authors list and click on a group of authors I get all books displayed.
I see (sorry don't have screenshot)
>(little face) 1 - 100 
When I click on  it displays all books by all authors.
When I sort by name and expand the authors list and click on a group of authors I get all books by authors last name first letter displayed.
>(little face) A
When I click on  it displays only books by authors whose last name begins with A.
I am clicking on the sublist itself not on the > to expand it.
I can expand the list and click (or CTL click)on each author but this is a very slow process as after about 8 clicks calibre does not respond for 30+seconds (using I5 second generation laptop).
I know that calibre knows the number of books per author as it displays the list in the tag browser, but I do not knoww the proper way to type this in the searchbar.
Thanks for the reply. Any other ideas?