Why is there a Invoice asset with a 0 value in a Realized Mark to Market download?

In a Realized MTM report there is an asset type 'Invoice'. It always has a 0 quantity. What does the asset type 'Invoice' means?

This appears when there is a P&L correction recorded for invoices that are received/processed after the delivery is realized.  So the delivery is realized and has an asset in the realized P&L section. The invoice asset is the balance of the accrued vs the actual invoice value on the realized asset.