Assigning default values during input model definition

I have a (small, recent) termbase. When adding terms on the fly during translation in Studio, I'd like the job no. to be added by default to each new term. If I try to make the relevant settings in the input model, the "Next" button is grayed out, so all I can to is "Cancel".

What am I doing wrong?

This is a screenshot of what I see, below is a screenshot of my termbase definition:

 

 

 

I'd be really grateful if somebody could point me in the right direction.

Thanks in advance,

Eva