Multiple NIRs getting created while updating item through FBDI

Summary: Need to create a single NIR for multiple items being imported through FBDI

Content (please ensure you mask any confidential information): We are trying to import mutiple items through FBDI using PIMDH source system. The requirement is that a single NIR should be created for all the items in a batch (Batch size is less then 20)

We have set following paramters for PIMDH source system in Manage Spoke Systems task: -

New Item Request: One per Batch

Associate: Create New

Name: NIR001

Add all items: unchecked

Effective Date: Effective Immediately

When we are importing item with above configuration, multiple NIRs are getting created instead of a single NIR. Is there a setup we are missing?