When installing lowering springs, coilovers, or any other product that lowers the car, the conventional wisdom is that you should wait and drive the car around for a while for the car to completely "settle." In reality, the springs won't, or should not, change height over time. The car will need to be rolled to neutralize the tire position before the height of the car can me measured, but this has nothing to do with the springs! It happens every single time the car is lifted off the ground.