If you look in the NHP hardware guide under the unpacking and assembly section 3.6, look in section 2 under DAQ system. You have a UDI PD2-AO-16/16 (i.e. 16 channels, 16-bit) AO card, and you have the NI PCI-6503 DIO card.

There is no analog input card typically for NHPs, because no one has ever asked for one. And for a bilateral NHP system there are no spare PCI slots. But there is no reason why you could not add it, because your real-time computer has one empty PCI slot. We typically use the 6229 card. There is a driver for it in xPC Target, it is 16-bit, good speed, 32-channels and is a good price. You would probably want to also get a BNC-2090a breakout box (and the cable too).