MG-811 CO2 sensor

when I checked the voltage espruino return now I've got 0.88volt when start and sensor is warmed, and 0.72volt when I blow on it

var co2 = analogRead(A5)*3.3;

when used this code

var co2=1-analogRead(pin);
var ppm=400+co2*(10000-400)

I've got readings at about 7400ppm, I fixed it but just for 400ppm level

var co2 = 1 - analogRead(A5);
 var ppm = 400 + co2*(10000-400);
  console.log(co2);
  console.log(ppm*0.054163846);

can't get readings of about 10000ppm when voltage on the sensor is 0.72volt