Please refer to the MAX31865 datasheet (Rev 3 7/15). Page 15 displays RTD MSBs and LSBs (01h-02h).
These two registers has a total of 16 bits combined, with the LSB being fault bit. The first 15 bits gives the ADC code (in decimal). Based on the formula on page 19, the equivalent resistance is
For example, in figure 3 from the MAX31865evkit datasheet below, 0x5075 in Raw RTD Conversion Data column translates to an ADC code of 10298 in decimal after taking into account of the fault bit. By default, Rref of the evkit is 4kohms. Therefore, RRTD = 10298 * 4k/(2^15) = 1257.0801 ohms as shown in the Resistance (ohm) column.