To show the relationship between the serving size and the number of pounds of meat needed for a lasagna recipe, a catering company uses the chart below.

Lasagna
Serving size
Pounds of meat
20
2
40
6
80
8
120
12

The employee who created the chart made an error when computing the number of pounds of meat for one of the serving sizes. For which serving size is the ratio of size to pounds of meat different from the other ratios?