Explanation

Scenario: By default, all releases must remain available for 30 days, except for production releases, which must be kept for 60 days.
Box 1: Set the default retention policy to 30 days
The Global default retention policy sets the default retention values for all the build pipelines. Authors of build pipelines can override these values.
Box 2: Set the stage retention policy to 60 days
You may want to retain more releases that have been deployed to specific stages.
References: https://docs.microsoft.com/en-us/azure/devops/pipelines/policies/retention