The headings font-size by default are set to percentage which is based on your body font size.
h1 is set to
400% so if your body font size is
10px, h1 400% equevalent will be
We made it like this so it is mobile responsive but if you need to change this you will have to override it using
You can add the code below in
Theme Options > CSS
Change the font-size as you like.