Please check: order price quantity set automatically

What causes this issue?

The system has calculated the order price quantity from the conversion
factor in the purchase order and the invoice quantity entered and
automatically set this quantity in the field <LS>Quantity OPUn</>.

How to fix this error?

Check whether the proposed order price quantity corresponds to the order
price quantity in the invoice. If not, change the order price quantity
in the field <LS>Quantity OPUn</>.
If you change the order price quantity, the system checks
whether the difference in the order price quantity is within the allowed
tolerances
whether the price variance is within the allowed tolerances.
(Changing the order price quantity results in a price variance since
<ZG>invoice price = invoice amount : order price quantity</>).

Error message extract from SAP system. Copyright SAP SE.