typos in https://github.com/PJLab-ADG/nr3d_lib/blob/main/docs/pack_ops.md

[tornadomeet]

https://github.com/PJLab-ADG/nr3d_lib/blob/main/media/pack_ops/packed_diff.png https://github.com/PJLab-ADG/nr3d_lib/blob/main/media/pack_ops/packed_diff_appends.png

hello, thanks for the great tutorials! in the above two picture, when the input feats of 6 and 3, the output should be -3 not 3 there?