Use of Chapter and Subchapter Titles

I’m on V2.2 on MacOS…

My binder looks like this :

CHAPTER ONE
Untitled
CHAPTER TWO
Untitled

When I compile for Print or EPUB, I get

CHAPTER ONE

Chapter Subtitle

Question : If I rename the “Untitled” scrivening to “Cool Name”, I get the same output as if I never changed the Untitled to Cool Name. I still get the CHAPTER NUMBER followed by the generic Chapter Subtitle.

Is there a formatting option I am neglecting to set?

Many thanks!