If you login to your Google Search Console account and click on the Search Analytics, you will vertical line on April 27, 2016 that says “update.” When you click on the learn more link there, it takes you to this page which explains Google updated how they calculate some of the search analytics impressions and clicks in that report. Google said there it impacts mobile apps the most.
But John Mueller of Google added that for the first time, the Search Analytics report now includes Knowledge Panel, in various Rich Snippets, and in the local results in Search as impressions when a URL shows up in those places. It seems Google did not count those before.
Get more information at: https://www.seroundtable.com/google-search-analytics-report-update-line-22057.html