Font size definition for 1st paragraph in stylesheet?

I'm using a style sheet that I've inherited from a person that is not available any more for a request. Moreover, I neither have a black belt in Asciidoctor nor CSS.
The stylesheet I'm using is outputting the first paragraph in a different font size than all other paragraphs. For waht do I have to search the stylesheet to adjust this?
Unfortunately, the stylesheet is quite big and seems to have a lot of abandoned defintions.
Thank you in advance!