2.1.1582 Part 1 Section 188.8.131.52, graphicFrame (Graphic Frame)
a. The standard allows a graphicFrame to be specified within a Chart Drawing.
Office does not support the display of graphic frames inside charts.
b. The standard states that the values of the macro attribute are defined by the XML Schema string datatype.
Office requires that the macro attribute value follow the same grammar as name-references ("[ISO/IEC-29500-1] §184.108.40.206") with a minimum length of 0 characters and a maximum length of 256 characters.