The source – support.google.com
On April 6, the algorithm for counting image impressions in search results in Google Search Console was improved. This information has been added to the Data Anomalies page.
We are talking about a more accurate calculation of the number of image impressions when the search type "Image" is specified in the performance report. So a slight decrease in the number of image impressions in the performance report can be ignored. The rankings were not affected by this update either.