Why do 3 elements with css property flex-wrap wrap to a new line?

Question

css

There are six elements that have a width of 33.33333%. I set display: flex and flex-wrap: wrap, but instead of laying out 3 elements in a row, only 2 elements come out in one line, and the rest are wrapped. Maybe something is wrong?

Answer 1

*, ::after, ::before {
    box-sizing: border-box;
}