This indicates the "write-in designation default" needs to be cross referenced.  Use the steps below to properly cross-reference that field:
  1. Go to Data Management
  2. Click Luminate Configuration
  3. Click Cross References
  4. Click Configure next to Gift Designation
  5. Find cross reference called "write-in designation default" and click Configure (Or Create)
  6. Chose the External Mappings Designation
  7. Click Finish