Hi-
One easy way to work this out is from the web form. Navigate to http://demo3/QdabraWebService/ on the server where DBXL is installed. Then click on the link for the Active Directory Service, and then click on GetAllUsers.
Page 25 of this document has some information on GetAllUsers:
http://www.infopathdev.com/files/folders/others/entry56816.aspx
In the case of our LDAP, I can use OU=SBSUsers,OU=Users,OU=MyBusiness, but I guess AD is different in each instance.
Have you tried modifying the value of Max Count?