little bit of horizantal scrolling last step

[exlhost]

Using latest whmcs with twenty ten as child theme and standard cart as order form the user is able to scroll a bit horizontally on mobile at the last page of the checkout where you have to fill in your details or log in.

The amount of horizontal scroll is small but I would like to remove it.

Anyone has a solution?

i think somewhere of the standard cart or theme an element is exceeding the width of its parent element.
 

Thanks