It depends on which game you are playing. Since you are playing Pokemon Platinum, you should get the following message:
"It's very friendly toward you. I can tell you treat it kindly."
Remember, just because you have the message doesn't mean you have a high enough friendship value to evolve it. The message appears at 200-254 friendship, Crobat takes 220 to evolve.
An in-depth article on friendship here.