See where you take it as a reference. If the left and right margins are set asymmetrically, the editing area is not in the middle of the whole page, so it is normal for the header to be unevenly distributed horizontally. The key is that it is aligned with the editing area. If it is not aligned with the editing area, you can double-click the header to enter the header editing state, set the paragraph format of the header, and set the left and right indents to 0.