The reason why these parameters are introduced to the model

Dear Sir,
When I make the replication of the code, I wonder the reason why these parameters,gamman gammak dyratio, are introduced to the model. The accessory is the code and corresponding model.

Note: When I delete the term containing gamman or gammak in the labor/capital income tax equation, error occurs. (17.4 KB)

These parameter encode the debt feedback to make sure the government stays solvent.