The ADC value at 0v volts is approx 65,536 and then decreases to 0 as the voltage is increased until approx 3v, and then will reset again to 65,536 then decrease again to 0 for 3-6V. So I can only measure over the 3v range.
Trying to change the gain has no affect.
I am using a raspberrypi.
ie
i2cget -y 1 0x49 0x00 w