Most progressive springs work by having a smaller gap between a portion of the coils so they bind which cause the wider portions of the springs to stiffen up and increase the spring rate. Understand that a spring is a torsion bar than is curved into a coil. The wire twists from one end to the other. Twisting a short wire of a given diameter is harder than twisting a longer one over the same angular distance, so shorter wire make stiffer springs. The spring wire itself is the same diameter from end to end, which, if all the coil spacing is the same, the coils will bind at the same time, have an equal spring rate throughout the distance of the stroke. By closing the space for a few coils at the end of the spring, which prevents them from twisting any more and that makes a shorter functional spring (wire), increasing the spring rate. Some shock manufacturers will use a short softer spring on top of a longer stiffer one. It give a similar result, with a little more abrupt transition between the harder and softer rates.
It doesn't really matter which way they are put on, but I usually put the closer coils on the top where the shaft is to possibly keep a bit of dirt out.
Bare