Also, the web site selection table shows the input of the AD7609 as 10 and 20V pk-pk, which should be 20 and 40V pk-pk
By way of contrast, the related AD7608 single ended part has the same advertised 10 and 20V pk-pk input, but twice the gain in its volts to code transfer function. So, one or the other is incorrect.
I find the use of the datasheet's +/-5V or +/-10V true differential input terminology to be confusing in this context.