The exercise asks for a program that translate elevator button presses to actual floors assuming that buttons 13 and 14 are removed. A program that subtracts 2 if the button is greater than 12 should get the right answer--assuming buttons 13 and 14 are missing.  But the test cases include presses for missing buttons 13 and 14. Those are not a reasonable test cases. The correct answers for those cases are error messages, not floor numbers.