The only way Acoustic Campaign can differentiate Leads and Contacts is by using the CRM Contact Type field. However, flexible databases that are not selected for CRM synchronization might not have this field. If a new record is added to Campaign first, versus CRM first, the default CRM Contact Type is a Lead.
To identify the Leads and Contacts we recommend building queries in Campaign that use both database fields. When you view the Edit Contact page for a particular contact in your database, you see values of Lead or Contact for the CRM Contact Type field. To create a query based on these values, use 1 for Leads and 2 for Contacts.