# Observing treatment traffic
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AWS AppConfig Agent collects aggregated treatment assignment counts and emits them as CloudWatch metrics in your account through a service-linked role that AWS AppConfig manages. There is no additional charge for these metrics.
+ Namespace: `AWS/AppConfig`
+ Metric name: `ReturnedCount`
+ Dimensions: application ID, environment ID, configuration profile ID, flag key, and variant

These metrics show how much traffic each treatment is receiving, which you can use as a real-time check that your experiment is operating as expected. For example, in a 50/50 A/B test, you can confirm that about half of entities are assigned to the control and about half to the treatment.

**Note**  
To emit experiment treatment traffic metrics to your account, you must opt in to the VendedMetrics account setting by using the `UpdateAccountSettings` operation. Vended metrics incur no additional cost.