2.1.1164 Part 1 Section 19.5.52, oleChartEl (Embedded Chart Element)
a. The standard places no restrictions on the relationship between the lvl attribute and the type attribute.
PowerPoint requires the lvl attribute be 0 if the type attribute is gridLegend.
b. The standard places no restrictions on the ordering and relationship of oleChartEl elements with respect to one another.
PowerPoint requires that all oleChartEl elements be stored in incremental ascending order (with no omissions) under one common par element for the animation to play properly.