File name specification when using iDOC as a source

I am trying to set up a batch job, using iDOCs from SAP CRM as a source.

I am familiar with the steps describing the configuration for real time scenarios, expertly described in

How to Receive IDOC in BODS from SAP (Outbound to SAP)

I am also aware the question has been asked before but was not answered:

Sending idocs from SAP ECC to Data Services

So, here is the same question again: What should I specify in the 'IDOC FILE' property of the IDOC object in my dataflow?

To me, it doesn't make sense as the source is CRM using a RFC interface, so why should I specify an IDOC FILE?

For references, here is my dataflow:

And below is the property on the IDOC object (I have included the object in the dataflow using option 'Make iDOC file source' instead of 'make idoc message source' - as I am trying to set up a batch job, not a real time job).

Any insights greatly appreciated.

Thanks,

Jan.