LTC1450L

Hi,

    I am trying to use LTC1450L for my application to give a +3V control voltage to an Attenuator, how to determine which of the two (marked in blue in the image above ) V in range is being used /or how to change it from one to the other, so that my V out is in range of 0 to 3V.

Using the first one i.e V in = 0 to 1.22 will give me a maximum of 2.4 V in the Vout, how do i use the second configuration i.e ( LTC1450L: Vin = 0 to 2.048 volts), i thought it might depend on Vcc but then, both of them have a maximum of 5.5v Vcc. Please Explain

Thank you