Missing contacts

Guys I have 28 contacts tagged and they should all be receiving mailers. However when I go in the campaign it only says there are 8 unique contacts. That means Im missing 20 somewhere. Any help?

Under Marketing → Reports I would first look at your tag application report to double check tag assignments to all the contacts (and when those assignments happened). That may seem overkill to check but when diagnosing/testing, always start by checking at the beginning of the process and working forward. Next, check your goal completion report in the same place. This will show what contacts completed what campaign goals. That will then give you a clearer informed frame of reference to determine why the 8 and not 28.