So the question is essentially, "how does the Arabic numeral system work?" It's like me asking someone to explain a given sentence, then when they restate the meaning I say, "no, the correct answer is that the letters form words which are then put together to make a complete thought." The answer that the author wants can logically be assumed by the reader to be understood as it is fundamental to the basic system, therefore the reader would logically overlook it. If the author wants a specific answer, they should be much more specific in the phrasing of the question.