The geometry causes the rear axle to move in specific curved paths. By tailoring your rear suspension's curves, you can control the axle movement and thereby tune your race car's performance. These curves can be set to cause the axle to steer to the right or the left.
Many racers are familiar with a common concept called anti-squat.
You should also use this same type of logic and examine the suspension from the rear view and make sure that you do not have pro-roll which can cause the left front tire to come off the ground in the corners. The Rear Suspension Geometry software is the only one on the market today that addresses 3 link and 4 link rear suspensions. Use the travel gauges with the software to see how spring changes affect your suspension curves. Without changing your linkages and only changing springs you can have axle oversteer or axle understeer depending on the spring change. The only way to know for certain is to use the Rear Suspension Geometry software.