Order price quantity exceeded by more than & %

The order price quantity (quantity in order price unit) varies from the
expected order price quantity. This depends on when the invoice was
received:
Goods received before invoice
The order price quantity specified in the invoice is compared with that
specified when the goods were received.
Invoice received before goods
The order price quantity specified in the invoice is compared with the
product of the invoice quantity and the conversion factor specified in
the purchase order.
INCLUDE MM_IV_MELDUNGEN OBJECT DOKU ID TX

System Response

The system has determined that the invoice quantity (in order price
unit) exceeds the expected order price quantity by more than the
tolerance for order price quantity variance set in the Customizing
system.
When you post the invoice, the system blocks the invoice with the
blocking reason "order price quantity variance"

How to fix this error?

Please check the order price quantity and make any necessary changes.
If you post the document in spite of the variance, the system will
effect the posting and the related account movements. The document
will, however, be flagged with a block indicator, which prevents it
from being paid.

Error message extract from SAP system. Copyright SAP SE.