When mirroring parts in an assembly and then generating a Parts List on the draft file of the assembly, the mirrored parts are shown as separate line items from the original parts. Why are the mirrored parts not summed up with the original parts in the Parts List?
Depending on your geometry, a mirrored part is not necessarily the same geometry as a rotation of the geometry. For some geometry, a mirrored part can result in geometry that then cannot be manufactured on the same tooling as the original part. This is why you have two separate line items in the Parts List.
If you want the mirrored part to be summed up with the original part in the Parts List, then use the Rotate option not the Mirror option.
Notes and References
OS Version: 1064