Google has posted about a data anomalies bug with the Search Analytics report found in the Google Search Console. The specific issue shows up when you use the “AMP non-rich results” search appearance filter and look at the clicks and impressions between December 14, 2017, and December 18, 2017.
Google said there “was an error in counting AMP non-rich results impressions and clicks” between those dates and you “might see a drop in your data during this period.” It did not impact the actual search results; it was just an analytics bug.
Here is what the report might look like for you:
The data should return to normal on or after December 19, 2017, but those few days will have some inaccurate data.