From your collection...

  1. Click on the inspector to open
  2. Click once on the collection on the page.
  3. 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.
  4. Change the Show at most to the number of items you want to display