The field AdditionalDonationFundID is a reference to the ID field on the BBNCDESIGNATIONIDMAP table. This creates a link between the BBIS and CRM designation.

https://www.blackbaud.com/files/support/guides/infinitytechref/Subsystems/dbo-4-0/dbo-4-0.htm#dbo-4-0/BBNCDESIGNATIONIDMAP.htm