For a list of the default attributes collected during an AD Discovery, please do the following:
1. Open the Configuration Manager
2. Under Discovery Management click Configuration
3. Click Manage attributes
4. Click Yes
5. Under Active Directory click Extend
6. Select the type of object (User, Group, Computer, Contact, Organizational Unit) and then click Get Schema
7. Check Only show selected attributes
All of the attributes with a grey check are the ones collected by default. If there are any blue checks, this is an extended attribute (one that was manually selected by a user to be included).