I suggest you look at the manual, it is well documented; what I am saying here is only what I recall and my not be entirely correct.
I assume you are using the outputs from the channels to digitize. These outputs are ±10V and were meant to drive a strip chart recorder. 10 V represents full scale for your measurement, that is, if the the sensitivity is set to 1V and you get 10V out you have a 1V signal. So in order to get the same value as the display you need to keep track of the sensitivity scale and scale your values.
Lastly, I am not sure of the update rate for this output, I think is kind of slow, ie, no more than 512Sa/s, it may depend on the time constant . So what I am trying to say, adjust your digitizing rate accordingly.
mcduff