If you need it lower use thinner upper spring isolators (#16), as you found,
The springs are "clocked", spring to isolators, but that isolator is free to be in any position (rotation) in the upper cup on the frame.
The lower end of the spring is also clocked to where it sits in the lower control arm and can be in only one position to sit at correct ride height.
The parts graphic shows an isolator for the lower end of the spring (#14) that looks simply like a pad for NVH. My car did not have those when I had to replace the broken stock springs.