Orchestrator - Updating Grid Values

Referencing this document -

E1: ORCH: How to Update Multiple Rows in a Grid? (Doc ID 2440613.1)

I understand how to use the RowNumberUpdate to indicate which row to update when returning multiple rows in a grid.  However, how could I indicate by Line Number (a field returned in my grid selection)  which  values to be updated?

I am creating an orchestration to voucher match and release retention on a subcontract (P4314).  I need to indicate by line number (PDLNID)  which lines to select to indicate an amount either to release or match.