There are two ways to set the serving size:

1. By specifying the serving size on top of the nutrition label and the equivalent of that serving size.

In this case, it is specify that each slice is equivalent to 166.6g

2. By setting the serving size blank, and specify the item pack size and the item weight.

In this case, the weight is set to 1,400g, pack size 1, and serving size is not specified, there fore, it uses the item weight as default serving size.