Some people use gutter to describe the space between 2 columns other use it to describe the space between two pages.
Indesign margins and gutter.
Gutter widths should relate to the body text leading value.
Choose layout margins and columns.
To achieve uniform spacing set your gutters to the same value as or a multiple of 1 5 or 2 for example the leading of the text.
Assuming i guessed correctly are you trying to define the gutter widthor gutter position.
To adjust column guides manually drag them horizontally to new positions producing unequal widths.
Open the pages panel window pages and select the thumbnails for the pages you wish to change.
Enter values for top bottom left and right margins as well as the number of columns and the gutter the space between columns.
Use margins and column guides to position content.
Indesign uses the first definition in margins and columns so i m going to guess that is what your question is about.
You can set the gutter size from the new document menu when creating a new indesign project.