Alright, so let's make both 7/8 and 3/10 into fractions with the same denominator. The lowest common denominator for both of these is 80. So, we multiply the top and bottom of 7/8 by 10, and the top and bottom of 3/10 by 8 to get fractions we can compare. So, we have 70/80 of a candy bar, and we want to make servings of 24/80 each. How many times can 24 go into 70? 2 times, with a remainder of 22. So, Tony can make 2 servings.
The whole idea of that kind of graph is that they allow you to view the complete distribution of data while also being able to see first and third quartiles, the median, and the minimums and maximums.