hello262 so thats in Figma and you wouldn't edit the mobile type sizes in that way - they are controlled with variable modes. So if you go to the left side nav in Figma and find the variables panel and then go to typography, you'll see desktop and mobile.
Then in your screens, with the frame selected, you'll see those modes.
If you are using a free version of Figma then none of that will show up, which is an unfortunately side-effect.
Let me know if what I've said makes sense or not - happy to expand.