FM8 DITA - Variables converting to text when generate book

I am using the built in DITA functionality for FM8. When I convert my .ditamap to a FM document (using the "Build FM Document From DITA Map" function) the document is fine including variables.

However, when I try to create a FM Book from a .ditamap (using the "Build FM DITABook from DITA Map file" function) the book generates and appears normal, however all of my user variables have been converted to text.

I have tried defining my variables (as: entity "CorpName" is fm variable;) in the book.rules.txt file with no luck.

Any ideas?

Thank you,
- Kevin