Grading of a complete exam with a passing percentage - Coursepress

When creating an exam at the end of the course, I'd like to be able to setup a passing criteria of 80%, but the current toolset seems to only allow you to set a passing grade per question, rather than for the set of questions as a whole.

For instance, if I have an exam with 10 questions on it, I'd like to let the student get a completed grade if they get 8 out of 10 of those questions correct, but they would have to answer all 10. I can set 80% for each question, but that won't work since each question will either be 0 or 100% since each question has only one answer possible.