You accumulate your CCA points and at the end, you'll be given a
grade, maximum is cut 2 points.
For poly, you can use the CCA to cut off the points ONLY if you
hit the min COP for that course.
For JC, you can just cut from your L1R5 if I'm not wrong.
For MI, you can use your CCA as a subject.
Also, good CCA points can also be used for interviews and
appeals, let them know you're outstanding (positively) in your
CCA.