Use those to limit the amount of suspension downtravel (or droop.) Here's how I would suggest that you set it.
Install a motor battery and everything else you run in the car except the body. Settle the car by pressing down on the chassis and let it come to a rest. Then, measure the ride height. Let's assume you're running a 5mm ride height. Gently raise the chassis from the middle of the front bumper and watch the point where one of the tires lifts off your workbench. Once you find the point that it lifts, measure the ride height again. Let's say it measures at 10mm. You subtract the two ride heights and come up with 5mm of droop. Do the same on the same side, rear wheel.
Now that you have that information, what do you do with it? First off, the amount of droop that you run greatly affects the amount of steering the car has. I would suggest starting with 3mm of droop up front. If you're not running swaybars, you might even go to 2mm of droop up front, but realize that it will reduce the amount of steering that you have compared to 3mm.
So, what you need to do is adjust the droop screw on the front wheel that you measured before and measure as before, until you get to 8mm height when the wheel lifts off the workbench. Once you have that done, lets' set the rear droop.
Get the car to resting ride height again and press down one front corner of the car and watch what the rear tire, on the same side as the corner you just set the droop on, does. What you want is to have enough droop so the tire never lifts off the workbench. I usually tighten the droop screw down until it does lift off the table, then back it off until it doesn't lift any more. If you go back and measure the rear droop the same way you did up front, you should end up with almost double the amount of droop that you have up front, so it should be somewhere around 5 or 6 mm.
At this point, you have the drrop set on one side of the car. What you need to do now is take all the rims off the car and rest the chassis on something that will lift it a little off the workbench, like a thin book or something like that. Back at the front corner that we just set the droop on, measure the distance between the lowest point of the arm and the work bench. Now you need to adjust the other side so that it is the same distance. Repeat in the rear using the corner that you previously set.
Once you get to the track, you might find that you have less steering than before and need to add a little more droop up front. It should be pretty good with 3mm droop up front, though. I hope that helps.