Worth keeping in mind that Facebook has manipulated data before:

https://en.wikipedia.org/wiki/Pivot_to_video#Facebook_metrics_controversy

In September 2016, Facebook admitted that it had reported artificially inflated numbers to its advertisers about how long viewers watched ads leading to an overestimation of 60-80%[44] Facebook apologized in an official statement and in multiple staff appearances at New York Advertising Week.[45][46] Two months later, Facebook disclosed additional discrepancies in audience metrics.[47][48] In October 2018, a California federal court unsealed the text of a class action lawsuit filed by advertisers against Facebook, alleging that Facebook had known since 2015 that its viewership numbers were inflated "by some 150 to 900 percent" and waited over a year before taking action to disclose or fix the problem, citing internal Facebook communications that "somehow there was no progress on the task for the year" and decisions to "obfuscate the fact that we screwed up the math."[49][50]