Add text to single form lightbox mode

I have successfully added text above the button/after the form fields in lightbox mode for my form, which is located in the footer of my site. However, I only want this message to appear in this form, and not others on the site. How do I target only this specific lightbox form? 

This is the code I used to add the text: 

.field-list:after {
    content: "I will never share or sell your information";
    display: block;
      margin-bottom: 17px;
    font-family: inconsolata;
      font-style: italic;
    white-space: pre-wrap;
      opacity: .55;
  }