A ratio used in formulas for computing the amount of variable
bandwidth to be allocated. Valid values are 1-255 which is the
numerator of a fraction whose fixed denominator is 256. Thus
the value 255 is really 255/256 the most conservative value;
the value 1 is really 1/256 the most liberal value; the value
128 is really 128/256 or 50%. The default is 50%.