short call is not defined, I think the contract says something like "prompty available." However, it is generally accepted to be two hours. Long call is a 12 hour call out.

The reserve trip assignment process is based on a score, called the RAW score. Stands for reserve assignment weighting or some nonsense like that. Anyway, its basically a score showing how much you have flown. When it comes time to give out trips, the pilot with the lowest RAW score is given the trip.