Checkout, Changing the size of the ‘Special Instru.’ box.

I have a two language cart and have noticed on the Japanese side, for Step 2 of the Checkout section, PART of the ‘Continue to Step 3 - to confirm your order‘ text is scrunched up on the right side of the Special Instructions.... Box.

Currently the width of that box seems to be set at about 90 percent of the width of the total space available. My solution would be to make it 100 percent, which will force the text below and left, where it should be.

I have had a look through my main CSS but could not find anything in the store section that I could match to the box. Could anyone point me in the right direction as to what to change? Or suggest another solution?

Thanks!