All of these properties and methods are explained in the Word Help. You can access it when you right click on the property or invoke node in LabVIEW.
"Index Required Variant. The name or index number of a member of the collection. The index can be a numeric expression (a number from 1 to the value of the collection's Count property), a constant, or a string. For more information about using the Item method with a specific collection, see the Help topic for that collection."
In the Borders Set LineWidth VI is where the Borders>>Item Index invoke node is being set. Since you are documenting the VI for others to use it, I would suggest you modify this VI:
Usually, when you wire -1 to a "counting" node, such as index, it would mean all. However,
some methods are different. I would suggest you delete the numeric input to this node, right click on the node, and create a control. It will not create a numeric, but the actual name of that element. It will be displayed in a Text Ring. This would be easier for everyone to understand. You can also right click on this control and choose to show Digital Display. This will tell you which index corresponds to which name. For some reason, who ever designed this methods in Microsoft, decided to have negative indexes.
Similar for Style property. Much better approach is to use the text ring instead of the numeric input.
Zvezdana S.