Hello Steve,
The pinout is contained inside the NI Digital Waveform Generator/Analyzer Help.chm file. From your post, you already have this file, however the latest version can be found here. You should be able to open this on most Windows based PCs.
If you open the chm file and look under Devices >> NI 656x >> Channel Interface >> Front Panel and Connector Pinout (this is probably what you have printed) you will find the connector pinout.
One item to be careful of is the pinout changes if you connect up the standard cable (192744-01). If you use this cable the pinout reverses at the other end of the cable. This is explained just under the picture of the connector in the section I mentioned above. It says the following:
If you design a custom cabling solution with connector (779157-01) and cable
(192744-01), the NI 656x pinout is reversed at the end connector. For
example, the signal shown on pin 1 shown in the previous figure would map to pin
73 at the end connector.
This matches what you are seeing. If the pinout reverses DIO 0 becomes DIO 15.
I hope this helps,
Jesse O. | National Instruments R&D