What is the logic behind these?

[sshable]

s_mpii_2_smpl_jt = [
6, 3, 2,
-1, 4, 1,
-1, 5, 0,
-1, -1, -1,
8, -1, -1,
-1,
13, 12,
14, 11,
15, 10,
-1, -1
]
s_3dhp_2_smpl_jt = [
4, -1, -1,
-1, 19, 24,
-1, 20, 25,
-1, -1, -1, # TODO: foot point
5, -1, -1,
-1,
9, 14,
10, 15,
11, 16,
-1, -1, # 23
# 7,
# -1, -1,
# 21, 26
]
s_coco_2_smpl_jt = [
-1, -1, -1,
-1, 13, 14,
-1, 15, 16,
-1, -1, -1,
-1, -1, -1,
-1,
5, 6,
7, 8,
9, 10,
-1, -1
]

also for cocoeft.py
why this same variable is different?
s_coco_2_smpl_jt = [
-1, 11, 12,
-1, 13, 14,
-1, 15, 16,
-1, -1, -1,
-1, -1, -1,
-1,
5, 6,
7, 8,
9, 10,
-1, -1
]