Google has made a change related to how they calculate your website’s Top Search Queries.
The update is designed to showcase more accurate information about the rankings of your web pages.
Previously we reported the average position of all URLs from your site for a given query. As of today, we’ll instead average only the top position that a URL from your site appeared in.
Let’s say Nick searched for [bacon] and URLs from your site appeared in positions 3, 6, and 12. Jane also searched for [bacon] and URLs from your site appeared in positions 5 and 9. Previously, we would have averaged all these positions together and shown an Average Position of 7. Going forward, we’ll only average the highest position your site appeared in for each search (3 for Nick’s search and 5 for Jane’s search), for an Average Position of 4.
Google clarified that historical data would not change.