Custom Text Overlapping Itself on Mobile

Site URL: https://polygon-oriole-cdcg.squarespace.com/

I'm using a custom font on this site but on mobile, the text overlaps itself. Why is this happening and what is the solution to this?? It's the h4 font that is having the error...

Here is my line of code for mobile font:

@media only screen and (max-width: 640px) 
{h1
{font-size: 30px;
  line-height:50px
}

  h4 {font-size:clamp(4px, 6vw, 10px);
   font-weight: 600;
  letter-spacing: .30em;
  line-height:.01px;
} }

Hi

Your site is private. Can you setup password & share url again?