Credit Memo Journal Line types

Hi,

We are working on customizing SLA rule for AR Invoices and AR Credit Memos to default a constant receivable account based on a particular "Bill to Customer Country"

Can somebody tell me the difference between the below two Journal Line types which are available under Event Class "Credit Memo"

Credit Memo Default Receivable

Credit Memo Default Application

Do i need to customize both or one of them?

Regards,

Arvind