Translation:I got a high grade on an exam, not understanding the subject.
Yeah, exactly. It's another one of those that is technically correct, but it's not the common way to put it.
Incidentally, I only really posted this comment because my original answer, "I got a good grade", which to me sounds more correct even though it is not the literal translation, was rejected as incorrect.
This is a complex sentence that does not easily translate into nice flowing English. Like others I had a translation that was rejected but seemed to be a better way of expressing the idea. It is not really a problem as it is possible to see the wording preferred by the course and, although it might be considered clumsy, it at least provides insight into the grammatical logic (a comment that applies equally to other sentences elsewhere in the course).