NIH has a firm requirement that recharge funds cannot be used to offset write-offs (https://grants.nih.gov/grants/policy/nihgps/html5/section_7/7.9_allowability_of_costs_activities.htm – search bad debts).

For NUcore, leave the quantity as is and set the cost to zero and reconcile rather than cancel the order. They should then document how the difference was covered (other external business preferred).