они фиксированы, 0.75 дюйма...
In Microsoft Excel, the header and footer on your worksheet always use a left and right margin of 0.75 inch. Because of this functionality, left-aligned text in the header or footer always begins printing 0.75 inches from the left edge of the page, regardless of the left margin setting. Similarly, right-aligned text always begins 0.75 inches from the right side of the page.
In Microsoft Excel, the header and footer on your worksheet always use a left and right margin of 0.75 inch. Because of this functionality, left-aligned text in the header or footer always begins printing 0.75 inches from the left edge of the page, regardless of the left margin setting. Similarly, right-aligned text always begins 0.75 inches from the right side of the page.