MEMS CO Sensor Datasheet is incomplete

The datasheet for this part states that package is sensitive to CO between 5 -5000ppm, but provides no equation on how to translate to that scale.

I have seen comments on this forum stating this part cannot give an accurate PPM count. That was understood when buying the part as this is clearly stated. 

I am not asking for a precise number - a relative reading between 5 and 5000 is fine.

I am asking for guidance on the intended way to translate a voltage or ADC Value into the relative scale of 5 to 5000ppm, as the datasheet is not at all clear on how to do this.

For example - one presumes the following:

Vin = ADC_value / ADC Resolution * Vref

3) If there is some other intended translation, please provide it.

Thank you.