I found this FAQ from https://www.toptal.com/designers/subtlepatterns/
FAQ: Can I use the patterns in themes I make and sell on ThemeForest or similar sites?
Yes, but please credit Subtle Patterns in your theme description or source code.
- What does this “your theme description” mean?
Themeforest theme description page?
Or, CSS file theme description like description:……?
- How to credit in source code?
Thanks in advance.