Email Program Audience count is different than delivered/bounced email count.
The Audience number doesn't refresh or update once the Smart List is created, so the number of qualified people can change between then and sending the email. That is normal. If you want to double check the people, you can click the refresh button on the Audience pane of the email program just before sending, or create a separate Smart List with the same filters just before you send the email.
Also be aware that the Audience may include duplicate leads, or leads that have reached their communication limit. These leads will not show as blocked, but will not be sent the email