"Document item" in V_V2

Hello!

in the rescheduling sort criteria, there is "document item" (to set the priority to).

What does it do? Does it read the Item number?

Another question is: if i want to set up the rescheduling not to prioritise PO over SO, and other way around either, is it enough to set priority "5" to document category? Will it reschedule in paralel if i set up Date of creation as priority 1, delivery priority as 2, and document number as 3? I am afraid, having 2 different number ranges for PO and SO, it will start prioritising one of them because if the number range anyway?

Thanks in advance for advice!!

cheers,

Bea