The total reach for the month of February doesn't add up to the total that I'm seeing in the source system i.e. Facebook Ads. I've tried refreshing the data but it's still wrong. This doesn't make sense because the rest of the data is accurate.
Reach : The number of people who saw your ads at least once. Reach is different from impressions, which may include multiple views of your ads by the same people.
Reach is a unique metric and it should be used very carefully. Depending on how reach is pulled from the API, it’s possible that the reach values will not match the UI for a selected date range unlike other metrics (impressions, cost, etc.). The API can return reach at varying levels of granularity based on your reporting requirements. Typically, when we pull Facebook Ads data, we pull the data at a daily level of aggregation. When this is done, the reach metric is locked in at the daily level of aggregation and for the combination of other dimensions pulled with it (ad, device, etc.).
Let’s illustrate this with an example - If you’re viewing ads data for a 7-day span and a user sees an ad each of those days, the UI will count that as 1, however the API will return the count of 1 for each of those 7 days since the data is pulled on a daily aggregate. The UI performs dynamically and de-duplicates this data.
If you do not plan to use reach at the daily level, then we can work with you to get a data set setup to align with the aggregation level that you plan to report reach at. Reach can be pulled in many different increments. Some examples of those increments are lifetime, 7-days, 30-days, last month, this month, last quarter and this quarter.
To learn more about why the unique reporting metrics may not add up, please review this article by Facebook. I hope this article was helpful! Let us know if you have any questions or feedback to help make this article better. Thanks!