(credit: Marco Paköeningrat Follow)

On Friday, Facebook took to its official blog to confirm and respond to a Wall Street Journal report that describes how one of Facebook’s most crucial metrics for measuring video-view performance was wildly inflated for two years.

The blog post, from Facebook VP of marketing David Fischer, spells out exactly what the company did wrong. Its advertising-dashboard measure of “average duration of video viewed” was apparently based on questionable math. To get that count, the “total time spent watching a video” was only divided by the number of people who have seen at least three seconds of the video rather than everyone who watched the entire video.

Fischer writes: