I am not sure if I calculated it correctly. What I understand is LSB = (Voltage range)/2^(bit).
I also tried to do some calculation following the decription of absolute accuracy in your data sheet. What I got is:
NI6132: AbsoluteAccuracy at 1.25V is ~ 700uV
NI6289: at 0.1V is 30uV.
I know that it is not fair to compare since they are at different voltage range. So my basic question becomes: is NI6132 good to measure signal ~ 100uV (or lower) accurately compared with NI6289?