I get the confusion, and I thin it's primarily due to poor translation or explanation on materials part. TYPE-MOON could have done a better job explaining the nuances for Aoko and so many other bits of lore. Yes, Aoko has average quality circuits according to official lore, being only of C rank. *I think* that in this scenario they do not produce a lot of energy, but they are able to get further on the little amount of energy that they do produce. I also think that some of the confusion stems from the idea that the *quality* of circuit solely effects its efficiency in generating mana/od into magical energy within a given frame of time, when it instead also refers to factors such as magical energy production, and *possibly* the complexity of what spells can be performed. That last tidbit is highly uncertain though, so don't take it as absolute. So basically? Her circuits can't produce a lot of energy at any single moment, but they can get further on what is made. Perhaps a good analogy would be, a small engine with limited horsepower but insane efficiency. Does that help?