change font size in markdown for mobile view

Site URL: https://www.travisvoice.com/about

how do I edit the text size for a mark down box for mobile view? Ive already added syntax for the markdown box for desktop view including font size, weight, and style, but its too large for mobile

desktop vs current mobile view

Add to Page Settings > Advanced > Header

<style>
  @media screen and (max-width:640px) {
  .markdown-block span strong {
    font-size: 25px;
}
    
  }
</style>