code examples are not using column width

[wolski]

The code example isn't using the column width, (see image).

This is the yaml section for my poster.

column_numbers: 4
poster_height: "1009mm"
poster_width: "1426mm"
title_textsize: "75pt"
author_textsize: "35pt"
font_family: Monaco
primary_colour: "cornflowerblue"
secondary_colour: "darkblue"
accent_colour: "slateblue"
titletext_fontfamily: Arial
logoleft_name: hexstrickerPRL2.png
logoright_name: FGCZLogo.png
output:
posterdown::posterdown_html
bibliography: bibliography.bib

Is there a way to increase the width of the code chunks?