Hi Bill-
The NI 625x Specifications include this info. They can be found from the USB-6259 product page. You can also query this information programmatically, either from the DAQmx Device Property Node (LabVIEW) or the DAQmxGetDevAIVoltageRngs() and DAQmxGetDevAOVoltageRngs() (C API).
Hopefully this helps-
Tom W
National Instruments