In SA mission exercise

https://academy.pega.com/mission/system-architect/v4/exercise/in/29826

In US-2006 task

1. In  data page D_RentalcustomerSavable, there are 2 parameters defined, 2nd one is "Count", pls refer to below picture.

And the property "Customer" pass "1" to the parameter "Count" when calling the data page.

Wonder what's the purpose of this parameter?  I can not find any use of "Count" inside the data page.

2. In Data transform "SetCustomerKey", in the "Pages & Classes" setting, two page names are defined as below picture:

Wonder what's the purpose of 2nd one "D_RentalCustomer"? It's not used at all inside the Data Transform.

Thanks!