The ADC of the MAX31865 is 15bit, and the register 01~02h in table 9 is a 16-bit value. The least signficant bit is a Fault bit that indicates whether any RTD faults have been detected. It's not part of the measured data. Therefore, to get the actual ADC code, the value of register 01~02h in table 9 must be shifted by 1 bit to the right.