Understanding List Stats

Contacts: Number of contacts in the list. Contacts can be added to the list via Signup Forms, Bulk import, API. 
Subscribed: Number of contacts in Subscribed state. Campaigns can be sent only to contacts with Subscribed state. 
Non-Subscribed: Number of contacts in Non-Subscribed state. Contacts added from Signup Forms (with Double Opt-In setting enabled), will have Non-Subscribed state until the contact confirm by clicking the Double Opt-In link sent to them. 
Unsubscribed: Number of contacts who have unsubscribed from receiving any further emails. 
Bounced: Number of contacts to whom the emails delivery has failed (hard bounced). We will stop sending further emails to contact from the moment it is hard bounced.
Sometimes email delivery failure could be temporary (soft bounced). In such case, any further emails to the contact will be sent. We will mark the contact as bounced when the email delivery fails continuously 7 times or more in more than 7 days.
Complained: Number of contacts who have reported SPAM or Abuse complaint as response to any of emails sent earlier.