The magic number 103.64, which when multiplied with the difference in pension pre 24 Sep 2012 and revised pension wef 24 Sep2012, will give you your arrears.
So forget those Rank Wise Tables, separate for Pension/FP and again for Non-AMC/AMC/ADC/MNS; just remember 103.64 * (Difference in Basic Pension Pre 24Sep 2012 and presently Drawn).
As an example, if difference in pension is (27795-26050) = Rs 1745
Amount due = 1745 * 103.64 = Rs 180851.
Multiplication factor 103.64 takes into account DA changes, over period for which arrears are calculated.
The formula is not an approximation and gives amount within an error of up to plus/minus Rs 10/-; that is because of truncation of 103.64 to two decimal places.
If arrears are because of Pension & FP, or if during intervening period you are getting additional pension by virtue of being 80, 85, 90, 95, 100; the amount will have to be worked out case by case.