Format of the data in the subdural ECoG dataset

Hello, We were working with the dataset in the title. We were wondering about the format of the X,Y,Z positions presented in the accompanied paper. In the paper the results are reported over a single X,Y,Z tracking, however, the dataset has multiple points for tracking the hands. Which dataset is the ones that you used for the paper. Thanks a lot

The motion data

Regarding the motion data, we created a sagittal plane centered at the body by using the left and right shoulder markers, and decoded the position of the wrist marker relative to the body-centered coordinate (see the attached figure).

body-centered coordinate