The Galileo board is using voltage dividers on the analog inputs as shown in the schematics (Intel® Galileo Schematic) on sheet 18. It's using 2x 4.99K Ohm 1% resistors per channel.
If you are just measuring a voltage output, you don't need to think about this, but if you are using voltage dividers in your circuit with the analog inputs, you should take these resistors into account, when calculating the component values.
Brilliant - so the Gallileo halves the voltages before they hit the ADC - great! Having the complete circuit diagram always helps