How to change the size of “1 thought on ‘blogpost” in the comments section?

I would like to change the size of the Heading “1 thought on …” in the comments section. How can I do this?

I see that one option is going into the customizer and change the size of Heading 3 to do that (“1 thought on” is marked as Heading 3), but I would like my Heading 3 to remain the same because I need it for my posts, and only this text to have a different, smaller size.

Is it possible to do this?

Thank you!