Why is the left and right margins inconsistent when the margin or padding values are displayed on the mobile terminal?

I usually work on pc-related projects, but suddenly I can"t find my way in some places where I need to change the mobile terminal.
as shown in the figure, I add margin: 030px to the m-body, or to the padding value in the figure, the content of the m-body is not centered, and the distance on the left side is too large and the right side is too small. How is this going on?

Apr.09,2021

you see if padding is added to your parent element


you need to check your upper and lower element styles carefully. There is no problem alone.


found the problem. The DOM structure checked one by one, and found that a code copied by the package div was caused by locating the negative value on the right. It is a low-level error. We should check it carefully and ask questions again in the future. Thank you both upstairs

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