I think you are misunderstanding how calculting it works
Dual wingebeat (lets just say one hit we will make it two later) has 40 bp.
Technician mutliplies that by 1.2
Stab multiplies by 1.5
Item multiplies by 1.2
You get 86.4 about
Multiplying that by two, you get 172.8
Because of communative property, you can rearrange this in any order and still get The same answer.