Site-content width mobile Twenty Twelve

Hi,

Styles for Twenty Twelve shows a smaller site-content on mobile device/screen then without Styles. So the white area around the tekst in active Styles is larger then normal.

On my large monitor and Ipad both, with and without Styles shows the same width of site-content area and white area around the tekst.

How can I change Styles, css or … so the width of the text on a mobile screen is the same as in the default.

I hope someone helps me, have search and s …

Regards
Loek