What they mean is by no means really bad for your family. China has this tradition since ancient times. There is a mirror in front of the house. The function of this mirror is to defend against monsters. Because when the monster comes, you can see it in the mirror and scare yourself away. There is indeed a saying that this place in our village has a similar tradition, which is not true for the people in front of his house. It's okay

But these are folk customs and have no scientific basis.