Hi,
Do you mean the number – Total delivered in the Insights tab does not equal to the number of the contacts in the subscription list?
If yes, this is a normal phenomenon.
First of all, the number of the subscription list member is changing dynamically and not a fixed value, since there will be new subscribers and unsubscribers.
The total delivered number means the number of emails delivered successfully. In other word, there are also unsuccessful attempts to deliver. For example, the Hard bounces and Soft bounces in your screenshot.
The specific delivery and failure categories can be seen in the Insights tab of the certain Marketing Email.
Please refer to the following documentation to know more about the Insights of Marketing Email.
Glossary of common insights terms (Dynamics 365 Marketing) | Microsoft Docs
