It means that you have a very subtle sense of humor. You find things amusing that a lot of people don't. When you tell a joke, or when you find something funny, you generally don't show a lot of dramatic outward signs that you think it's funny. Whether that's good or bad is in the opinion of the person saying it.
An example that illustrates the difference is to compare a British comedy like Fawlty Towers to an American comedy show like Newheart. The shows have very similar background situations (innkeeper couple, friends, and guests) but because of the difference between British comedy and American comedy, the styles of humor are VERY different. I think they're **both** funny, but that's probably because I'm one of the "dry humor" types like yourself.
Your vote on this answer has already been received
2 Guys Coming Out Of The
Examination Hall With Chips
And Coke In Hands.
1st Guy:- Which Paper Was Its?
2nd Guy:-i Thinks Maths....
You Read The Question Paper?
2nd Guys:-no I See A Girl
Sittings Beside Me Using Calculator.