Future issues of this nature can be prevented by ensuring the sell quantity is in single units rather than cases if you intend to sell ship single units, or ensure the delta scanners only pick full cases.
Sadly once the order is created, this cannot be fixed in the front end. To resolve this - our support team will need to investigate, run scripts or liaise with the hosting or development teams. Any Issues with contacting us, please see the following Get support in Dimensions.