Tailored Audience processing may take up to 24 hours to complete. While an audience change is processing the existing audience to be updated is unaffected. We do not recommend making more than one update for additions and one update for removals per audience within this timeframe. Once the Tailored Audience is done processing, the size of your audience will be updated.
Tailored Audiences are processed in batches in the order that they come in and although they can take up to 24 hours to finish processing, more often than not this happens in significantly less time.