I don't think the carriage house is for sale. According to county records there are three units at this location. Unit B is what is being advertised for sale and includes the 2nd/3rd floors of the home pictured. Assuming Unit A is the ground floor, the carriage house would be Unit C.
If you are not currently working with an agent to ask your question of the listing agent, I would welcome the opportunity to earn your business. Give me a call so we can discuss what you are looking for in a home.
Best of luck,