When publishing an audience to Facebook there are several things to keep in mind:

If the Meta Business / Ad Manager Account you are publishing to is brand new (you haven't ran any campaigns on it yet), the audience will publish, but will be grayed out until Meta has approved the Business Manager or Ad Account. To be approved, you must spend on campaigns and follow their policies for several weeks.

Once the audience is published to Facebook, the matching process begins almost immediately. The Mobile Ad IDs (MAIDs) you sent from Onspot will be matched with their associated Facebook profiles. You will see an initial "Estimated Audience Size" range that will begin to populate as the matching process continues.

Published audiences can take up to 24-48 hours to fully populate. If a device becomes active in Facebook it will be included in the audience.

In our experience, match rates between the MAID count in OnSpot and estimated audience size in Meta is around 20%. This can vary depending on the audience type, recency (how long is the lookback time period) and any filtering that was applied.

**Note that Estimated Audience Size is just that - an estimate, and can vary depending on factors such as: