XBee S2 Analog Pin readings

I have an XBee S2 router installed on both a Jaycon systems Explorer Board & an adapter board. Pins 0 thru 3 are set to Analog [2]. At this point I don’t have any sensors attached just configured. The samples that I’m receiving indicate about a .6 voltage. I was expecting around 0.
Does this mean the sensors that I install can only register an additional .6?

unless you figure out what is introducing the additional voltage that would be correct.

Thank You for your time.