Partial posting packing slip using X++

I found the snippet code that post the packing slip using X++ using SalesFormLetter shown below.

However, I would like to partially post the packing slip ( i.e. not fully packed/delivered ).

How could I modify the code in order to do that ?

        SalesFormLetter salesFormLetter;
        salesTable      salesTable;

        salesTable = SalesTable::find('SO-000000175');

        salesFormLetter = SalesFormLetter::construct(
            DocumentStatus::PackingSlip);

        salesFormLetter.update(
            salesTable,
            systemDateGet(),
            SalesUpdate::All,
            AccountOrder::None,
            NoYes::No,
            NoYes::Yes);