Those styles may be placed in anothewr part of yhour themes styles.
Rather than changing the themes styles.css, it will be a better option to make changes in another file as "custom.css". SO you cahnges won't be effected by any updates atc.
Your code snippet shows the styles for the "columns" property, but as I tried to define the div structure from your site,
That div has 3 classes: four, columns, gdl-left-sidebar
Your pasted codes are only for the "gdl-left-sidebar.columns" class,
but the width property is controlled by the "four" class.
So if you change thet property as you wish, you can see the effect in your pages.
Try using some browser extensions such as Firefox's FireBUg or Chrome's Developer Tools...