Where does Excel store the parameters you pass into Range.Group - excel

Question

This has to do with Pivot Tables.
I am trying use VBA (or C#) to get to some data that's stored in the spreadsheet, but I don't know where it is in the object model. I know the data is in the spreadsheet because when I unzip the spreadsheet, I see it in the pivotcache. The following documentation for OpenXML talks about the field in particular:
https://msdn.microsoft.com/en-us/library/documentformat.openxml.spreadsheet.rangeproperties%28v=office.14%29.aspx
In the RangeProperties class, see the groupInterval property, in particular.
For instance, the XML shows:
<fieldGroup base="0">
<rangePr startNum="19" endNum="947" groupInterval="656"/>
<groupItems count="4">
<s v="<19"/>
<s v="19-684"/>
<s v="685-1350"/>
<s v=">1351"/>
</groupItems>
</fieldGroup>
But I don't know how to get to this from the Excel object-model at runtime.
The above data represents the entries the user makes in order to group a set of rows in a pivot table. Below are more details on how to get to it.
When you click on Rows of a Pivot Table, you can Group the rows. For instance, let's say you have a thousand rows, but the values range from 1-100. You don't want to see all 1000 rows, just in 10 rows (groups of 100). First group will be a row that aggregates all the rows where the value is between 1-100, the next group for values 100-200, etc.
When you right-click any cell the Row Labels section, and click on the Group item from the context menu, you'll get a small dialog box with "Grouping" in the title bar, and fields:
- Starting at:
- Ending at:
- By:
And there will be a checkbox next to the starting at and ending end fields.
I'll take the defaults, and increment by 100
The equivalent to doing this in VBA (or C# VSTS) is:
Select the cell:
Call the Group() method on the current single-cell selection, eg:
Selection.Range.Group true, true, 100
At this point, the PivotItems associated with the PivotField end up with captions such as "1-100".
Now, if you right-click on the field again and select the Group item, you will get the same dialog box pop-up, with the fields of the dialog box filled in with the previous values you selected for that PivotTable.
However, the information that's used to fill that dialog box doesn't seem to exist anywhere in the object model. I suspect I just don't know where to look.
Does anyone know?
So the basic question in is, when I call the Group method on a single-cell Range object, and pass in various parameters, where are those parameters retained in the object model? I know it's there because Excel itself is able to load it up and it's stored in the spreadsheet.