The 3 column layout supports 3 equally proportioned columns. If you need a more complicated 3 column layout, then you can always nest 2 columns Fibonacci and place a further two columns within a column.

You can of course modify column width with CSS if you want, preferably by adding an extra CSS class.

Three columns layout example

col1

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

col2

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

col3

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.