Explanation

Box 1: The email will be blocked, and the user will receive the policy tip: Message blocked.
If you've created DLP policies in the Exchange admin center, those policies will continue to work side by side with any policies for email that you create in the Security & Compliance Center. But note that rules created in the Exchange admin center take precedence. All Exchange mail flow rules are processed first, and then the DLP rules from the Security & Compliance Center are processed.
Box 2: The email will be allowed, and the user will receive the policy tip: Message contains sensitive data.
Reference:
https://docs.microsoft.com/en-us/microsoft-365/compliance/how-dlp-works-between-admin-centers