How to make Product Grid width 80% of screen size

[Nyanko]

How do I make a Product Grid's width 80% of the screen size with custom CSS?

The CSS should go directly into the custom CSS field on the Product Grid and not in the theme CSS itself.

[BSS-Commerce]

Hi @Nyanko ,
Can you kindly share your store link (with the password, if any) with us? We will check it and suggest you a solution if possible.