Jeffrey, this is how I take it:
On Xflow interface, if you would like to show the "heat/weather" of certain group, you enter the group in the "Group" field
of the heat record. And if you think below or equal to index X the weather is Sunny(green, good), then enter value X in the "Threshold - Minimum" field and if you think any tickets with index larger than Y the weather is Stormy(red, bad), then
enter value Y in the "Threshold - Maximum" of the heat record. And what factors contribute to the index? check the "Heat Attributes" tab of the heat record...you will see what fields and how they contribute to the calculation of the heat index
and you can even change those factors/attributes to fix your specific business requirements.
Thanks _Chi