Credit memo accounting has unearned revenue lines but the original trx associated with CM does not

Summary:

When a single-period revenue scheduling used is applied to invoice lines, Invoice accounting as expected (Receivable DR, Revenue+Tax Cr). However when a Credit memo is issued against the same invoice, the accounting for the credit memo includes a debit an d a creditof an equal amount to Unearned revvenue. Why are these unearned revenue lines created on the Credit Memo when there is no invoice on the lines? I will include screenshots of the invoice and credit memo.

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