Since the Pedestal can be a Positive or Negative number, it is written in 2's complement so that when binary addition is used to add it to the actual offset, the result is correct. A positive 2's complement number is the binary equivalent of the number. A negative 2's complement number is the binary equivalent of a number that when added to the positive version of the same value, equals zero. Remember, for pedestal correction, the 13th bit is the sign bit.
Adding a 2's complement Example: 2 + (-2) = 0, [
0000 0000 0010 + 1111 1111 1110 = 1 0000 0000 0000]
Looking at the first 12 bits of data since the 13th bit is ignored, 2 + 4094 = 4096 or 0 for 12 bits of Data