Person 1: My boss really hasn't got a slightest idea how to run a company .
Person 2: Tell me about it! My boss is as incompetent as yours.
Person 1:I had a terrible day!
Person 2:Oh,Tell me about it! (Person 2 doesn't want Person 1 to tell about his day. He/she just means that he/she had a bad day too.)
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