Basically Google is changing how AMP error reports works. More or fewer AMP errors as can be seen on the vertical update line of the Google Search Console report, effective from the 19th of September 2016, marks a significant change in the way the new Google AMP handles error report.
Again, Google’s AMP error report in the Google Search Console now scans for AMP errors differently from the way it used to scan errors. The update has available on the data anomalies page of Google reads “you might see a fluctuation in your AMP data, due to a change in our scanning process.”
And no, these few changes to the AMP error report will not impact ranking or indexing as it is only an “internal change”, John Mueller of Google added on Twitter. “It is just a reporting change in the Google Search Console AMP error report. It is an internal change; it doesn’t affect indexing/ranking.”