Credit memo Replication to ECC

Hi,

Am working on complaints and returns scenario.

Where am able to replicate Returns, substitute delivery to ECC and do the delivery, billing..etc

I want to replicate 'Credit Memo request' from CRM to ECC and do the billing.

Below are the configurations i did.

CRM:

Created complaint, from complaint created Credit memo.

For item category , COMP, G2N, 'external billing' is set

ECC:

Item category determination

Copy control

Copied the entry of CR-CRMC and created new entry with CR -CMR.

In the item level maintained additional 2 item categoris of G2N, REN (kept all items of CR-CRMC combination)

Now the issue is

Am able to replicate 'Credit memo request' from CRM to ECC, but in the Item quantity it is showing Blank.

Please help me to rectify the issue and replicate the 'Credit memo request' do Billing.

Thanks in advance