Trying to change width of the post page in blog

[BhargavRajGuru]

I have created at root following directory;

layouts/_default/single.html

Now I am modifying this single.html file to change the width of the write-up in my post page of blog.

I have modified this <div class="mx-auto flex max-w-screen-xl"> to <div class="mx-auto flex max-w-screen-2xl">

But now when I inspect this in chrome, I don't see css style loading for 2xl, whereas it is loading for xl.

Why is it so?

What is happening here and if I am doing something wrong, please tell me the correct way to do it.