[Publish] Why doesn't my data match between Buffer Publish Analytics and Facebook Analytics?

This article relates to the Overview Report under Analytics.

The Overview Report includes a Post Performance table, showing aggregate metrics for all posts sent during the selected date range, including posts sent outside of Buffer.

For Facebook specifically, the numbers you see here could be higher than what you would see within Facebook Insights. This is because the Facebook API provides the total count of metrics that have ever happened, as opposed to within Facebook, which shows the metrics that you have permission to view (e.g. certain shares), either through the privacy of the user, or as the post has been deleted.