In the Apple Summary Sales Report using App Store Connect API, you can get a daily count of downloads and re-downloads by using the 1F and 3F values in the Product Type Identifier column. You can then cross check the download numbers against the downloads reported in the Analytics section of App Store Connect. When looking at a month of data, the first time download numbers seem to line up exactly ("1F" in the API versus "First-Time Downloads" in Appstore Store Connect). There is a discrepancy though between reported re-downloads. The total units for "3F" does not line up with the "Redownloads" numbers reported in the Analytics section of App Store Connect. The "3F" redownloads from the API appear to be 60% higher for a month compared to the App Store Connect reporting interface.
What could be going on here? Is there some type of de-duplication process run on the App Store Connect web report data that is not run on the data coming out of the App Store Connect API? Any insight would be greatly appreciated.