From your collection...
- Click on the inspector to open
- Click once on the collection on the page.
- Click on the tool on the inspector that's on the far right. This should show the Titles & Summaries interface. If it doesn't, make sure you click on the Titles and Summary box on the page (2). If you've double-clicked on that, click off of the item and then reselct by clicking once.
- Change the Show at most to the number of items you want to display