Topic Score Has Changed
The Topic Score from the "Optimize" tab will show a percentage score measuring the frequency of certain words appearing in the sources pulled vs. the mentions in your editor's content.
There is a 1-2 percent (or so) swing that is normal for this type of scoring algorithm, and if you notice larger fluctuations after several days, it could be the results had been refreshed to reflect an updated SERP via Google's API, or if the sources in the Research tab have been manually changed, then the score will change as well.