The total of the quantities entered exceeds the open quantity

What causes this issue?

The total achieved by adding the quantity to be billed to the quantity
reset exceeds the open quantity.

System Response

The system determines the rejected amount by comparing the open
quantity, quantity to be billed, and quantity reset. In the current
instance, the resulting quantity is negative.
INCLUDE NA_ALLG_VERARBEITUNG OBJECT DOKU ID TX

Error message extract from SAP system. Copyright SAP SE.