When using the Last Auth + Profile Link merge rule in Adobe Audience Manager, there are a few reasons why the segment population might be inflated:
Merging of authenticated and anonymous profiles: The Last Auth + Profile Link merge rule combines both authenticated users (users who have logged in) and anonymous users (users who have not logged in) into a single profile. This means that if a user has both an authenticated and an anonymous profile, they might be counted twice in the segment population.
Overlapping IDs: If the trait you onboarded has overlapping IDs or multiple IDs assigned to the same user, this might also cause the segment population to be inflated.
Real-time updates and data latency: Adobe Audience Manager processes real-time and batch data at different intervals. It's possible that the segment population is still updating, and you might see fluctuations in the numbers due to data latency.
To troubleshoot the inflated segment population, you can try the following:
Check the trait qualification rules and data source mapping to ensure there are no overlapping IDs or duplicate user counts.
Monitor the segment population over time to see if the numbers stabilize as real-time and batch data are processed.
Experiment with different profile merge rules to see how they impact the segment population. For example, you can try using a rule that only considers authenticated users to see if it results in a more accurate count.
If you're still facing issues with inflated segment population, consider reaching out to Adobe support for further assistance.
Remember that segment populations can sometimes be different from the actual audience size due to factors such as data processing times, user attrition, and profile merge rules. Make sure to monitor and analyze your segment populations regularly to ensure the accuracy of your audience targeting.