Cannot change field width

Hi, I am currently trying to edit this form as in the 'Medicare Number' section, the fields are WAY too wide and going off the page/past the forms column width. 

I've tried several ways to fix it with the CSS codes I am finding on your support page but just can't seem to reduce the width at all. 

On this contact details form, there are 3 x 'Medicare Number' sections that are all like this and i'm not sure why. Could I have these made smaller? 

You may add this custom CSS in your form

#customFieldFrame_57{
width:500px !important;
}
You may adjust the width to your preferred size.

Guide:https://www.jotform.com/help/117-How-to-Inject-Custom-CSS-Codes

Please give it a  try and let us know how it goes.