one in a million

I just got an email from my health insurance company thanking me for being 'one in a million' and then I got to thinking about it. is it really a compliment to be one in a million? 'cause that can be taken in two different ways meaning completely opposite things. one the one hand, it could mean that you're the only one like that, special, unique. on the other hand, it could also mean that you are one of a million or the same as all the others. just another way the wonderful english language screws with your head I guess so the next time you say something idiomatic, make sure what you intended to say only has one meaning.