About PGA112 gain calculate confuse

Hi Ti,

Im JD from Taiwan.

I had two question about PGA112.

<1> Document issue

PGA112 datasheet ,page 36 table 9

I calculate the Maximum Signal by  Page 33   Vout = G x Vin -  AVdd /2 x(G -1).

I calculate the Max Signal and result is Vout =2 x 2.25 -3/2 x (2-1) = 3 V, Im confuse why document result is 2.95V. 

<2>Design issue 

Our company had design a small current detect ion current(1uA to 100uA)PCB. 

Detect mode are 1uA and 100 uA.

We detect 100uA is no problem normally. 

When We detect 1uA current the result are 0.98uA   normally.

But when we change other PGA112 to self test 1uA mode,the result are different ,maybe 1.00 or 1.01uA or 1.02 on the same PCB,some PGA112 is above the average(0.98).

I know the PGA112 gain tolerance is very small.

but this issue is going to make our energy map shift.

Thanks .