What does the Exchange 2010 Mailbox Role Calculator mean by the total number of Highly Available Database Copy Instances (Includes Active Copy) within DAG?

My company is at present upgrading from Exchange 2003 to Exchange 2010 and implementing a site resilient solution involving two sites which will host Exchange servers. We are currently trying to estimate what our storage needs will be when we move from Exchange 2003 to Exchange 2010. Below is a breakdown of proposed number of users and also their mailbox limits:

Mailbox Limit:                            50 MB                  100MB            250MB
Site 1 Number of Users:            1600                    300                  100
Site 2 Number of Users:            2700                  300                  100
User Group:                  Normal end users      Management            Executive

Can anyone recommend when it comes to the use of the Exchange 2010 Mailbox Role calculator what does it mean when it asks the following question:

Total number of Highly Available Database Copy Instances (Includes Active Copy) within DAG?

Our initial plan is to have a site resilient solution which involves 4 Exchange servers within our single DAG which will be operating in Active/Active mode and will have 3 types of database copies (an active copy, passive copy and a copy of the other site database).

 When it comes to the question asked by the calculator what does it actually mean by total number of Highly Available Database Copy Instances (Includes Active Copy) within DAG:

(4 servers * 3 types of database copies) = 12 copies or just simply the 3 types of database copies?