Why have you chosen mean=100 and std=50

[venu1666]

scale keypoints to be centered around 0 with a range of [-1, 1]
# mean = 100, sqrt = 50, so, pts should be (pts - 100)/50
key_pts_copy = (key_pts_copy - 100)/50.0

In the above code why mean=100 and std=50,from where and how to calculate those values?