Amazon itself mentions this “ Amazon acknowledges that minor discrepancies between data displayed in the Advertising Console and API reports may occur. These discrepancies are expected due to the inherent differences in traffic validation and data refresh processes. However, these discrepancies should not exceed 5% under normal circumstances “
​ https://advertising.amazon.com/API/docs/en-us/guides/reporting/v2/advertising-console#discrepancies:~:text=and%20summary%20reports.-,Discrepancies,-Small%20data%20discrepancies