It means it will cost you two table service credits. Sometimes its used around here to refer to restaurants that are a little more dressier and have better food (but that isn't Disney's definition). Most signature restaurants are the Deluxe Hotel's "nice" restaurant - but there are a few park restaurants that are signature (CRT - which is only two credits because of its popularity, Bistro d Paris and Brown Derby),
Le Cellier and Coral Reef were both two credit restaurants originally on the plan.