If I do badly, may I retake the Exam, since I don't  want to take a non-credit course or a course that doesn't satisfy the general education requirement in  mathematics? :

No.  The exams have been designed and tested nationally so that repeated sittings for the exam  will result in the same placement and almost always nearly the same score.  Only in extenuating  circumstances and with the permission of the chair of the Mathematics Department can the exam be retaken.  As indicated by a message on the computer screen when you take the exam, results of retakes will be ignored  unless permission is previously obtained .