If all he said, after a conversation, was a parting remark, "See you," it really means nothing more than "good-bye." Taken literally, he is saying "I'll see you again later" - but that's just an idiom. If someone says "See you" to you when parting, you wouldn't ask, "Great! When?" back (well, you might if you were I, but then I like to stir it a bit with idioms). You would just say, "Yeah!" and leave, without an expectation of an imminent future encounter.