Why are a minimum of four treatments needed for Vanquish?

Hello. I am wondering--for a very low-fat area such as arms or upper abs (where one only wants to lose half an inch of fat mass at most), are four Vanquish treatments really necessary, or would one or two Vanquish treatments suffice? Are the results of Vanquish just additive, with each treatment chipping away more at the fat layer, or does the effectiveness of the treatment overall rely upon multiple treatments in succession, due to some biological factors?