To change it you need to edit CSS respectively:
line 916, margin-left: 70px; – to adjust left margin
line 929, max-width: 580px; – to determine width of entry-content
I know that it is a month old post, but if you already figured that out it might help somebody else.
But those changes will affect posts width, so it is posible only with static pages, if you have a post site it will require additional editing of post layout.
It was easiest way to achieve this for me, because i use custom post layout with removed right panel.
