Larger values give larger bulbs. Negative values give a bulb on the other side of the plane. When zero, the bulb is like a sphere that just touches the plane. When positive, there is a crossover point. When negative the bulb simply bulges out of the plane like a pimple.
Higher values make the top end of the bulb fatter.
The 2d strophid curve can be extruded in the Z direction or rotated about various axes by using the SOR parameters. Larger values give larger bulbs. Negative values give a bulb on the other side of the plane. When zero, the bulb is like a sphere that just touches the plane. When positive, there is a crossover point.