Only 3 Items appear in the summery block made to display my products

I'm building an online shop for my paintings on my website. I chose to display them in a summary block because I think it showcases them better in their aspect ratio. However, the summary block currently only shows the first 3 paintings in my inventory, and I'd like it to display around 15. Can you help me adjust the settings to show more products?

If you need to have a look at my web site it is in dev. You will need to use the password: "Karl" to view it. 

https://www.karllorenz.net/

Thanks!