TEMP36 temp. sensor

I have a doubt giving the correct formula for reading this sensor, this is the sensor's parameters:
Temperature range: -40C to 150C
Output range: 0.1V(-40C) to 2.0V(150C)

For converting the ADC value to mV the they use this equation: mV=(ADC value * 5000)/1024
My question is. the max. output voltage is 2.0v at 150C this gives an ADC value of around 409.
So I would change the first equation to: mV= (ADC value*2000)/409. Am I right?

http://arduino.cc/en/Reference/Map

or: