Arduino Nes controller, Please Help!

i think the reason why i cant isolate the "a" button is because i think the chip in the controller is doing math. for instance

the base number would be 127 - x (x being the value of the button)

so when i press the "a" button, in the serial monitor it comes out to 127
because 127 - 0 = 127 and therefor a = 0

when i press the "b" button, in the serial monitor it comes out to 126
because 127 - 1 = 126 and therefor b = 1

and so on.

im not sure how to approach this for a fix...