Underdelivery not allowed for final confirmation

Dear all,
Operation confirmation is generating un error:
- Underdelivery not allowed for final confirmation (check entry)
- Message N° RU036

overdelivery/ underdelivery tolerances are maintained in OPK4 as follows:

Underdelivery : X Error when quantity falls below underdelivery tolerance
Overdelivery: X Error when overdelivery tolerance is exceeded

Now the error appears in the following case:

Operation qty = 50

Yield = 45
Scrap = 5

Normally the sum of the yield and scrap quantity is 50 but couldn't confirm the operation, I have the error message RU036 (

Underdelivery not allowed for final confirmation (check entry))

Thanks in advance for your help