How to write @media queries so that they work correctly on pseudo-HD phone screens?

Question

Media queries

I usually limit the content width by setting a minimum width on the body tag by adding a meta tag
body { min-width: 480px; }

<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0">

On the current site, the minimum screen width is set to 480px.
But on the customer's phone, the site is displayed truncated. Only the initial 320px of the installed 480px is visible on the screen.
The customer's phone is normal - one of the new Xiaomi with a screen of at least 1280x720.
I suspect that the matter is in the installed meta tag and the pixel density of the Chinese screen.
Can someone come across?