The space comes from a few things.
– Empty Info bar. Hide the info bar in Main Options > Menus > Info bar > Hide Info bar
– 15px top padding on content that can be set to zero in Main options > Content Areas > Padding and Spacing > Content top box
– Default 1.625em space between Title and content that can be removed with a zero (or other value) in Main options > Content Areas > Padding and Spacing > Space between title and content box