what is production selection probability in ACT-R?

I have a problem with declarative and production in instance based learning based on ACT-R. I have a dataset. each record is a instance with some features and label. I want to give payoff for final decision. for example if label is 1 and decision is 0 I give payoff -5. to the best of my knowledge this payoff is for production. each record in my dataset is a chunk so what are the productions in my problem? how can I give payoff for specific production? this paper has an example but I really I don't understand what entities get payoff? as I know, productions get payoff. what are the productions in my problem and this paper? there are two probability: first for retrieving chunks and second for production selection in page 4 of this one. what does it mean?