correlation for multiline in NW BPM

Hi Experts,

This is related to NW-BPM not CC BPM.

My flow is like :

BPM (Asynch req) --> ECC

ECC (asynch response) --> BPM

In ECC validation is done and response (Asynch) is sent back to BPM.

In BPM --> ECC flow:

Request has multiple Items under a single PO

PO

   --> Item1

   --> Item2

etc ...

and response also has the same structure.

PO

   --> Item1

   --> Item2

I am defining a correlation in such a way that

response PO = request PO

and

response Item = Request Item

But as I have multiple Items ,

Do we need to explicitly provide multiline check like we have the option in receiver determination ? if yes where we can provide in NW-BPM case.

If not , will the correlation also checks for multiple Items or simply the first item?

Regards,

SP