default ADC value of beaglebone black is 3010-4090range why?

when i connect my beaglebone black industrial with usb cable and check the ADC count of analog pins using the commands
cd /sys/bus/iio/devices/iio:device0/cat in_voltage0_raw

it shows “4080”

cat in_Voltage1_raw
3077

etc
Why does the ADC count appear high when there is no input provided?

ADC inputs are high impedance, add a pull up, pull down resistor or a voltage divider (i.e. potentiometer)