Configure approval rules for Requisition using mapping set

I have created a mapping set and data set based on the documentation ( )

However, when configuring the approval rule, i saw the below in the documentation. My query is related to Starting participant, how do we identify which mappedapprovalattribute to use like 1,2,3,4 etc.. Also, is the constant value that we use except for changing the attribute values like 1,2,3,4 etc… Please confirm