[Freesurfer] Doubts on bblabel

Dear FS experts,

By definition  bblabel means..

Applies a bounding box to a label. The bounding box is specified by six coordinates (xmin,xmax,ymin,ymax,zmin,zmax). Only those label points within this box are copied to the output. If a min is not specified, then -infinity is used. If a max is not specified, then +infinity is used.

Example:

bblabel --l lh.G_cuneus.label --o lh.out.label \   --xmin 0 --ymax -90 --zmin 10 --zmax 20

Keeps label points from lh.G_cuneus.label that have x > 0, y > -90, and z between 10 and 20. The result is stored in lh.out.label.

IN THE ABOVE MENTIONED EXAMPLE, WHAT IS THE BASIS FOR THE SELECTION OF X, Y, Z VALUES??