First, you click on the Site Styles icon on the right of the Header
Next, you choose Fonts
Scroll down to the bottom and choose Assign Styles
Product Detail: Price
Scroll down to Product Detail Page > In Item Price > Click Heading
And then, click on the Heading 4 of the Size option
Next, you choose Custom
Finally, enter the custom size you want and click Save on the left of the Header
Product List: Price
Scroll down to Product: List > In List Price > Click Miscellaneous
And then, click on the Miscellaneous of the Size option
Next, you choose Custom
Finally, change to the custom size you want and click Save on the left of the Header
