RMCS Contracts are unable to group after Amend the Subscription

Summary:

Contract identification Rule says group by (Bill-to Cust & Document Id) for Subscription Source Doc.

System creating VRM Contract for the first time from OSS, However after we amend with Quantity change as a Material change ( CM ) system creating new VRM contract but not creation with the parent contract. while we amend the OSS contract we say

Revenue Management Rule: Create a New POB

Amendment Credit Method: Full

We are also coping the charges including adjustments.

So In order to get the single RMCS Contract even we amend the OSS what are the additional attributes need to pull in Identification Rule?