The cumulative received quantity from the delivery schedule is negative.

What causes this issue?

Sales scheduling agreement item &V1& &V2& has a delivery schedule with
&V4& as negative cumulative quantity received by customer.
There are two possible reasons for this:
Either a negative cumulative quantity was entered manually
Or the system determined a negative cumulative quantity based on
document &V3&.
In the case of the latter, it is likely that the document (last
delivery, consignment issue by external service agent, or outbound
delivery order) belongs to the last fiscal year.

System Response

The system issues a message. If this message is an error message, you
must correct the cumulative quantity received by the customer before you
can save the delivery schedule.

How to fix this error?

Check the cumulative quantity received by the customer and correct it if
necessary.
If the system determined the negative quantity because the &V3& document
entered belongs to the previous fiscal year, enter a valid cumulative
quantity received by the customer manually.
You might have to clear the corresponding quantity with a negative
correction delivery for the previous fiscal year and post it to the new
fiscal year with a positive correction delivery.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.