Explanation:

DLP stands for DataLossPrevention. A DLP policy is used to define exactly what constitutes a confidential email. For example: any email that has a credit card number of bank account number would be deemed to be confidential.
The DLP policy matches for sent mail report is used to display which emails contained content that matched a condition defined in a DLP policy. The DLP policy matches for sent mail report can be downloaded as a table that lists every single email that matched a DLP policy. This would identify in this question if the email did actually contain confidential information.
To identify whether the email message included the disclaimer, we need to view the "rule matches for sent mail" report. The disclaimer is added to an email by a transport rule. The rule defines which emails should have the disclaimer appended. A common example of this is all email sent to recipients outside the organization. By viewing the rule matches for sent mail, we can verify if the email in this question did match a rule and therefore did have the disclaimer appended.