Facebook said in a blog post published Wednesday that several of its advertising and marketing-related metrics have been miscalculated due to a variety of discrepancies and bugs.

The social networking giant identified four specific metric areas – Page Insights, full-length videos watched, time spent viewing publishers’ Instant Articles and referrals within the Facebook Analytics for Apps dashboard – that have all been misreported in some way or another.

For example, in Page Insights, Facebook said its 7-day summary in the overview dashboard will be 33 percent lower on average while 28-day summaries will be 55 percent lower. Also, the average time spent per article in Instant Articles has been over-reported by as much as eight percent since August 2015.

The findings don’t really have an impact on Facebook’s users. Instead, it’s the advertisers and marketers that are taking the hit as they’ve been led to believe that Facebook’s ad platform – and by proxy, their ad campaign – has been performing better than it actually has.

That’s kind of a big deal when you consider that advertising as a whole accounted for 78 percent of Facebook’s $7.01 billion in total revenue during the most recent quarter. Worse yet, this isn’t the first time Facebook has admitted it goofed metrics as the company revealed in September that it overestimated video view times by as much as 80 percent.

Facebook said today that it has been working for months to improve ad reporting and will continue to do so through the creation of a Measurement Council.