This is a quick post to describe the different numbers you may see on a Campaign in the Campaign Canvas. Hope this helps.
Segment Members - the number you see is the number that the Segment is currently returning. It's not the number of the total contacts added to the Campaign. Because a Segment can be dynamic (Criteria can change, new people added to your database etc...), this number can also change. It will change if you go into the Segment and view the number of Contacts that the Segment returns.
Email - This number tells you the number of contacts that have been excluded from getting the email. Contacts may be excluded if they have unsubscribed, hard bounced or received the email previously (based on how you have configured this step).If you happen to delete a Contact that was excluded from receiving an email, that Contact will still be represented as part of this number.