Graph builder "properties" comment

[#1]

Hello,

I am trying to use use GB. the script says 

Properties( 4

Properties( 1

etc...

Can anyone please help me understand what does the number mean? 4, 1 ??

[#2]

Most likely some indexes related to Legend Display / Legend Model / Legend Item / Legend Box.

For example << Get Item for LegendBox has Model ID and Model Index

Names Default To Here(1);

dt = Open("$SAMPLE_DATA/Big Class.jmp");
gb = Graph Builder(
	Variables(X(:height), Y(:weight), Overlay(:sex), Color(:age)),
	Elements(Points(X, Y, Legend(1)), Smoother(X, Y, Legend(2)))
);
lgnd = gb << Get Legend Display;
item = lgnd << Get Item(2, 1);
Print(item << Get Type);