Quantity entered larger than quantity to be debited

What causes this issue?

You selected the field <LS>Subsequent debit/credit</>. The quantity to
be debited/credited cannot be any greater than the quantity invoiced so
far.
If the invoice refers to a purchase order for services, no invoice has
obviously been posted for the order.

How to fix this error?

If no invoice has yet been posted, the invoice you are processing
cannot be processed as a subsequent debit/credit.
If an invoice has already been posted, you can post a subsequent debit/
credit: Correct your entry in the field <LS>Quantity</>.

Error message extract from SAP system. Copyright SAP SE.