Google has made another change to their Search Analytics in Google Search Console, specifically with how Google is accounting for clicks and impressions.  The date of the change was actually April 27, 2016.

John Mueller posted about it on Google+:

As a result, you may see a change in the click, impression, and CTR values shown there. For most sites, this change will be minimal. A significant part of this change will affect website properties with associated mobile app properties. Specifically, it involves accounting for clicks and impressions only to the associated application property rather than to the website. Other changes include how we count links shown in the Knowledge Panel, in various Rich Snippets, and in the local results in Search (which are now all counted as URL impressions).

So most sites probably won’t see a huge difference, but those with apps associated with the sites could see a more noticeable difference.

When you look at Search Analytics, you will also see a new added update line for April 27th, so it will be easy to see if there are more noticeable differences for any of your sites.

Google has also updated the Data Anomalies page:

April 27, 2016

We refined our standards for calculating clicks and impressions. As a result, you may see a change in the click, impression, and CTR values in the Search Analytics report. A significant part of this change will affect website properties with associated mobile app properties. Specifically, it involves accounting for clicks and impressions only to the associated application property rather than to the website.

So if you have noticed any changes starting around the 27th of April, this update might be responsible.