why top_region_index and bottom_region_index are variable in MAISI? #1908

Hi,

In the file of C4KC-KiTS_subset.json, I find that the values of top_region_index and bottom_region_index are variable rather than fixed, e.g., top_region_index might be [0,1,0,0] or [0,0,1,0], bottom_region_index might be [0,0,0,1] or [0,0,1,0] why?

Thanks a lot.