Shouldn't magnetic data also contain 3 axes data like accelerometer or gyro?

To whom it may concern,

When using numpy.load() to load the magnetic data,

(ex. 99c94dc769b5d96e|2018-10-12--20-13-54/7/processed_log/IMU/magnetometer/value)

there is only one axis data as shown below:

magn_val_arr.shape
(6013,)
magn_val_arr.size
6013

but accelerometer contains three axes data

accel_val_arr.shape
(6013, 3)
accel_val_arr.size
18039

Is data missing or do I load magnetic data incorrectly?

Thank you.