Translation:There are two exhibitions in the castle.
The meaning is the same, but that would be "Im Schloss gibt es zwei Ausstellungen." It's only a difference of sentence structuring.
fair was not accepted. It is because 'exhibition' is used for arts. furthermore there are subtle differences between 'fair' and 'exhibition'. usually the focus is different. in an exhibition it is to show something, in a fair it is to sell something.