What is sensor radius?
MSB means either 'most significant bit' or 'most significant byte' depending on context. Where the range is given as +/- 1000 LSB, it obviously means least significant bits. Where the bytes of memory are being identified, it means bytes.

The radius calibration is the distance between the axis of rotation, and the active point of the sensor. See US3470730 for a calibration method. The range, +/- 1000, are the max and min values that this parameter can be set to, or be interpretted correctly, notwithstanding that 2 bytes can hold numbers from -32768 to +32767.