This seems like a silly question to me but I am having a hard time understand a certain function in the PM system.

When a user deletes a PM that they send you, a notice is sent stating something along the lines of "User has deleted a message that was sent to you, you should go and delete this message also."

My confusion is the refrence. Is that sitting in place of a message (and so is poorly worded) is it attached to a message that was deleted but already sent and cached in my in box. If the latter is the case, then to which message would it refrence (the one immediately above or below it)