2.1.1462 Part 1 Section 18.104.22.168, headerFooter (Header and Footer)
a. The standard states that the alignWithMargins attribute specifies that the header and footer should align with the left and right margins of the chart.
In Office, a value of true for this attribute specifies that the left and right edges of the header and footer align with the left and right margins of chart. A value of false specifies the application will determine the alignment.