Mobile screen is "medium", but I expect "small"

[Outage55]

Hello,

My mobile has a screen size width of 412px and height of 915px.

The sass settings file has:
$breakpoints: (
"small": 0,
"medium": 640px,
"large": 1024px,
"xlarge": 1200px,
"xxlarge": 1440px,
);

Why does my mobile phone (Google Pixel 6) with a width of 412px use the medium styling? Isn't 412px smaller than 640px?

Apologies, when this question has been asked many times before, but searching gives a huge amount of other fitting results.

Regards,

Stefan

[Outage55]

It turned out that I need to add the Html viewport tag to get this to work:
<meta name="viewport" content="width=device-width, initial-scale=1" />