Google has been working for days to correct data in Google Ads reporting caused by a bug. The bug affected reports for April 30, May 1 and the initial hours of May 2.
Current status: Data through April 30 is now corrected. Google says it is still working on correcting reporting from 12:01am on May 1 to 4:00am May 2 (PDT).
Google will update the notice in the Google Ads web UI when everything is fixed.
Why you should care. You may now resume pulling your April monthly reports together now that the full-month of data is apparently correct.
Note that this warning does not show in the Google Ads app or Google Ads Editor. It does affect all Google Ads reporting interfaces and any reports downloaded using the AdWords API, Google Ads API and Google Ads Scripts.
Google says the bug did not affect automated bidding strategies.