All kind time of day! Tell me, how to understand the behavior of letter-spacing. When scaling the screen, letter-spacing remains unchanged. Here in the photo under the picture, "your shelf - upper" when you zoom the screen length is not changed
Why do you scale the browser screen? If you check the adaptability in the popular browsers have special tools to change the width layout in the browser.
If you, say, asked letter-spacing: 2px, why the letter-spacing should change when zooming? Reread how it works letter-spacing: https://webref.ru/css/letter-spacing