To do this task
Open the build transaction for the inventory assembly.
Enter a lower value in the Quantity to Build field.
Click Build & Close.
What happens when I rebuild the assembly?
Component inventory parts and subassemblies are increased in inventory and the
number of assemblies specified in the build definition are reduced by the difference of the original build quantity and the new one. If the build transaction you're
editing is pending, the changes you make do not affect the quantity on hand of
components and assembly items.
Important: QuickBooks does not track the quantity on hand of an assembly by specific build. This means that if you've already built the assembly more than once, you may have assemblies remaining from more than one build transaction. These assemblies are tracked as one quantity—even if you edited the components list between builds.
We recommend that you sell out of a quantity of assembly items before
editing the assembly's components list and rebuilding.