Clarification on System Gain Calibration

I need some more details on the system gain calbration-- I found a similar thread for the ad4114, and it seems like it has an answer but I'd still like a clarification:

I assume the 3.75*Vref to 10*Vref means for the internal 2.5V Vref I'll need to apply a ~10 to 25V voltage (due to the internal dividers) to the analog input pins for the gain, right? 

And this will set the voltage that codes as 0xFFFFFF right? Does this mean the decoding formula will need an addition scaling term? For instance if I calibrate at 12.5V, then there will need to be an additional 0.5 term in the code to value formula to make 0xFFFFFF decode as 12.5V?