Hi,
Open this CSS file:
/templates/gantry/html/com_virtuemart/assets/css/flexibleVM2Global.css
and find this CSS rule:
.FlexibleCSS3ButtonQuantity span.quantity-box, .FlexibleCSS3ButtonQuantity span.quantity-box input.quantity-input {
width: 60% !important;
.............
............. [continues]
and replace it with this:
.FlexibleCSS3ButtonQuantity span.quantity-box, .FlexibleCSS3ButtonQuantity span.quantity-box input.quantity-input {
width: 59% !important;
.............
............. [continues]
Regards.