If there is an option and a Calcutta, then what's the option for and what's the payback on the option?
The "option" is typically just a side pool for whoever wants to participate, just a way to...uh...back

..your dog for some extra money, winner take all, otherwise...

. Not everyone has to participate, but if you don't, and your dog wins, you don't get the option money.
In the Calcutta every dog will be "bought", if not by an individual, by the pen.
I know what the option and Calcutta is for, but have never seen a baying that had both! It either has one or the other!
I don't know. Maybe just trying to give people a chance to win more money.
That's what the Calcutta is for!