Hi gmparsons,
There could be many variable at play here. However at the base, our platform processes what is sent to us. We don’t make up data, we simply process the XML reports themselves. The most common variables to consider are that some reporters will report either wrong, or delayed data. Also, not all receivers report DMARC aggregate data, meaning the volume reported via aggregate reports can be smaller than the true volume sent by any given email source.
Those are the most common, but by no mean exhaustive and I would not be able to comment further without a thorough review of the sending data, received emails, and reported XML.
I hope this helps!
AM
