from memory, not much, they send back a very general report of why you got the marks you got, and that was about it.
like if your internal and external marks seem totally totally out of kilter, then you principle can request an inquiry into it, on top of you getting a clerical check.
basically, its just a way of showing your school acknowledges that your results seemed funky, and that your not just a disgruntled student with a higher opinion of yourself than is due to you in reality.