I have a very simple campaign with 1 email that has the "11" in the bubble on the email in the campaign canvas. Clicking on this number, I see the contacts who comprise this number and they all have an Unsubscribe or Bounceback associated with them. However, 11 does not match any tracking fields in the email's Insight report. Hard bouncebacks on that email in Insight = 45 and Unsubcribes = 5. Does anyone know what that number on the email in the campaign canvas is actually showing?
My guess would be that the "11" are people in your segment who were never sent the email because they were listed as a bounceback or were unsubscribed at the time you sent the message. The 45 bouncebacks and 5 unsubscribes from your report are those that were sent the message and then either bounced back or unsubscribed from receiving future emails.