Social media industry commentator and consultant Matt Navarra shared what appears to be part of an email from Facebook to page admins or social media managers in a tweet.

Bad news, social media managers…

Facebook is changing how it calculates organic impressions meaning it will likely show a decline.

Changes rolling out between Oct 17 – 28 pic.twitter.com/3QHuUqbCDZ

— Matt Navarra (@MattNavarra) October 17, 2019

Facebook had not responded to a request for comment at the time of this post.

In the text shared by Navarra, the social network issued an alert that it is updating the way it filters repeat organic page impressions to mirror the methodology it uses for ads.

Facebook said it began rolling out the change Thursday, and the rollout would continue through Oct. 28, so page admins may not be able to detect any changes until the process is complete.

The text read, “Specifically, we will be updating the time frame for which we filter out repeat organic impressions from a same person. As a result, you may see less organic impressions for your page and posts.”

The social network said metrics such as reach and engagement will not be affected, adding, “We are unable to provide any estimates for how this update may affect your page, if at all. Fluctuations in impressions for Facebook pages and posts continue to be normal, as impression counts can be influenced by many factors over time.”