1. The item in requirements has a different pack size to the item in the catalogue for that supplier.
You will need to change the purchase unit from the drop down in the requirements and ensure the product record in Prima is correct.
2. The sales unit and the purchase unit do not match.
You will need to carry out the same process.
If the pack size in the stock product is not set up correctly or the supplier has changed the pack size please see our page for this.