The number of Castle Points depends on the number of chests already added from the craft menu. These three types of chests have their own total Castle Point limit. You cannot receive Castle Points for more than 20 chests of this type. For this reason, if you have reached the limit for these types of chests, the number of Castle Points you receive may differ from their descriptions.
However, don't forget that you can get more Castle Points by adding other types of chests, such as Elegant Chests, Ice Chests, and others. These can be found in the store.