Hi @mmhgloba!
As I see you are using Tahoma font family, which seems to be one of the default font families operation systems use:
https://docs.microsoft.com/en-us/typography/font-list/tahoma
which means you are not calling in the font family, you are just using what’s available. As you see in that link, Tahoma only has 2 font weights, normal and bold. This means when you are using a CSS font weight, which isn’t available, the browser will decide how it will display it. Your mobile phone might be able to make the font skinnier, but Windows doesn’t seems to do that, so it will use “normal” font.
If for example you would rather use a Google font:
https://fonts.google.com/
then our code would call that font in with the selected weights:
https://smartslider.helpscoutdocs.com/article/1787-fonts
->
https://smartslider.helpscoutdocs.com/article/1787-fonts#style
so if you would use 300 font weight like this, with a Google font, that would have 300 font weight in every browser, as all browsers would use that font weighted font, what we call in.
