Fix products display under categories

Hello,

I would like to figure out why I am getting weird display results when uing the following code:

<h2>My First Category title</h2>
[product_category category=”small-areas” per_page=”12″ orderby=”name” order=”asc”]

<h2>My Second Category title</h2>
[product_category category=”large-areas” per_page=”12″ orderby=”name” order=”asc”]

The resulting display is as follows:
prod1 | prod2 | prod3
prod4
That is great but when there are more than 4 products the display becomes:
prod1 | prod2 | prod3
prod4
prod5

Can you help me figure out what the deal is?
Thank you!