How to create Flare.json like data with size information for zoomable sunburst with labels

Question

I have to create a json file like Flare.json for zoomable sunburst with label visualization.

On what basis the size value have to give for creating the json data file. I couldn't find any reference regarding size information. Is it a random value or is it node values or how to generate it..? Could anybody please upload a sample code to create the dynamic json file with size information?

http://bl.ocks.org/metmajer/5480307