This is used to add XML content to the Data node of the chart. This is useful if another property will not satisfy your configuration needs. The content will be appended to the Pointer node for each value in your chart. This usually negates the need to use Data Label/Tooltip/Marker/Animation Settings properties.
Example:
<label enabled="true">
<position placement_mode="ByPoint" x="50" y="15"/>
<format>% Complete: {%Value}{numDecimals:1}%</format>
<background enabled="false"/>
</label>
<animation enabled="true" start_time="0" duration="0.5" interpolation_type="Bounce"/>