NTO had an Enterprise 2.

To accurately identify subscribers who have unsubscribed from any of the child business units in an Enterprise 2.0 account, it is necessary to create data extracts of all subscribers within each child business unit. This approach ensures that unsubscribes specific to each business unit are captured.

Data Extracts: By creating data extracts within each child business unit, you can gather comprehensive unsubscribe data for all subscribers specific to each unit.

Salesforce Enterprise 2.0 Account Management