The grading kit has four sample bottles. In this image, they are the first, second, third, and fifth bottles from the left. The syrup is in the fourth bottle. If the syrup is darker than the lightest sample color, then it is graded as the darker color.
The lightest sample color is "Fancy".
The next darker color is "Medium Amber".
The next darker color is "Grade A".
The darkest color is "Dark Amber", which is "Grade B".
The only difference is the color of the syrup. Taste is totally a personal preference. The most popular is "Medium Amber", and the most desirable is "Fancy".