Sidebar width

Hi,

How can I change the sidebar width to something smaller, maybe 1/4 instead of 1/3 width?

I found this post: https://kriesi.at/support/topic/changing-the-sidebar-width-and-keeping-it-responsive/

And tried changing this as suggested:

$avia_config['layout']['fullsize'] 		= array('content' => 'twelve alpha', 'sidebar' => 'hidden', 	 'meta' => 'two alpha', 'entry' => 'eleven');
$avia_config['layout']['sidebar_left'] 	= array('content' => 'nine', 		 'sidebar' => 'three alpha' ,'meta' => 'two alpha', 'entry' => 'nine');
$avia_config['layout']['sidebar_right'] = array('content' => 'nine alpha',   'sidebar' => 'three alpha', 'meta' => 'two alpha', 'entry' => 'nine alpha');

But then my left sidebar turns much bigger and the content area is reduced…

I know nothing about coding, so I really need something to literally copy and paste!!

Thanks

Matt