Facebook admit their metrics are a bit crap (up to 100% at times)
http://newsroom.fb.com/news/2016/11/an-update-on-metrics-and-reporting/
Quote. For paid ads reports, we've moved to a stricter definition that only counts reach once the post enters the person's screen ("viewable impressions"). With the stricter definition, we estimate that reported reach will be 20% lower on average.
Does reported mean "paid" for those that use it?
My guess is it's all fucked up :-)
They had a new system in May, but who knows. Only good for us though.