Header is one part too far down

[Marcel]

The header is one part too far down. (If i disable this theme, it works fine)

Other themes i use for GitHub: (All from this Orga)

• Browser: Firefox Developer 77b9 (64-bit)
• Operating System: Windows 10
• Link to page with the issue: https://github.com/StylishThemes/GitHub-FixedHeader/issues (Desktop and Mobile)
• Screenshot:
  
  

On the second its hard to see.