I suppose you're talking about that or this:
From there, to limit it to a single page you could simply apply the code inside that page, rather than globally. Two ways of doing it, using a Code Block or Code Injection per Page, then just wrap the CSS code into HTML tags:
<style> your-css-goes-here </style>
Now, I'm no longer working with any kind of support, so I won't be able to help you further.