The load sensor must be fixed central under the car between car frame and car floor. With the adjusting screw on the end of the load sensor you can adjust the height (distance between car and car frame) of the sensor. The adjusting screw of the load sensor must always touch the car floor.
If the weight in the car increases, the distance will decrease between car frame and the car floor. Because of that increases the pressure on the load sensor and that will be evaluated from the load weighing unit.