I had a similar question when I wanted to erase the "website" text box in the Guestbook which came automatically with the program.  The answer I got was I had to export my project to a disk and manually in the code delete this.  I am sure you can do the same...export your project to a disk, find the shopping cart in the code and chance font size.  I'm not good with coding so this is all I can suggest.

Degele, when inserting the products in the page there is another tab in the screen: Settings.

In this tab you may easily configure the font, its size and color of the cart itens!