I have seen this questions several times recently.  During execution, any text that appears below the step in Italics represents any context variable that changed during that step execution.  In this case, a function call will set the callStyle variable allowing the execution engine to take the steps necessary to handle that execution type.  This allows us to determine that we are in a function, a root test, or event a private function.  While primary used by the internal execution engine, it can be used by implementers as well.

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