Hi vodocentar.rs,
Thanks for reaching to us.
There are 2 ways to do that:
1. In case you want to use Custom CSS code, then add below Custom CSS code to Theme Settings > Custom CSS > Global custom CSS
.wd-single-meta .product_meta span {
font-size: 15px;
}
2. In order to adjust font styles with more options, please navigate to Theme Settings > Typography > Advanced.
In this area, you can use Custom selector and assign elements like screenshot https://prnt.sc/QbybXLmLCxzA
Please read documentation also https://xtemos.com/docs-topic/advanced-typography-settings/
Regards,