Hi i am doing an aptitude test and the book that im practicing off has a question written exactly like this?

From the digits 0, 1, 2, ..., 9 write the largest possible number using four of them. Underneath write the smallest possible four-digit number that can be made with what is left. (You can only use a digit once.) subtract the second number from the first. Your answer is:............

Im wondering if the ... is suppose to be a number you can pick from your choice?