This has something to do with the quality of the mirror. The two mirrors in your house are uneven and become one mirror. If one side is a little concave, it will look fatter; If the other side is a little convex, it will look a little slender.

If you have to find a satisfactory answer,

① You can go to a large shopping mall, where the mirrors are of good quality, with wide light and orientation, and it will be more realistic to shine in the mirror field.

② Compare my photos and videos.

After comparison, I know which to believe.