This is due to a security permission within the Security Profile for the user.
To disable the ability to over-receive, you can enable "Do not allow Over Receiving". This is set in FinOps Administrator on the Security Profile.
To set this, follow these steps:
Log in to FinOps Administrator
Click on System Control.
Select Security Profiles.
Select the relevant Security profile (containing the users that you wish to set this for)
Click Edit.
Click on the Security tab.
Expand the "Purchasing" Node.
Click on "Receive Goods Options".
Click on "Do not Allow Over Receiving".
Click on Enable.
Click OK.
It is advised to take a backup of your database before making any changes and it is advisable to make the changes on a test database so the effect can be tested before applying to live.