The advertising for this board implies there are two single-ended inputs, and while there are two inputs and a GND connection, the ADS1114 is only a single channel device, single-ended or differential. The TI datasheet clearly states this at the top of page 5, and explains it in more detail on page 32 (read the first sentence of 10.1.2). Here is a link to the TI datasheet : http://www.ti.com/lit/ds/symlink/ads1114.pdf
Thank you, we have corrected the page.
Ryan