Chartbeat treats assignment of groups on a page basis. For example:
Say a page, `example.com/news/article.html`, has 100 concurrent readers, 90 of which pass along information that the page is in the “News” section, 8 of which don’t pass along group information, and 2 of which pass along the “Opinion” section (whether due to a changed group assignment, conflicting templates, or unexplained error).
Chartbeat will designate `example.com/news/article.html` as part of the News section, and all 100 concurrents will be counted towards that section.
Please note that it is still possible to assign multiple groups to the same page. Chartbeat will assign to the page the most common collection of groups. So if you tag a page with the following comma-delimited pair of authors: “Jane Doe, John Smith”, both Jane Doe and John Smith will be assigned to the page.