To modify how many items or articles are displayed in a blog layout, click MENUS from the top menu bar, and naviagate to the menu that the blog is attached to.
In my example below, the blog I want to modify is stored within the "Main Menu".
now select HOME from the menu:
Om the right hand side of the screen you will see the parameters for this menu item. It is here that you can spcecify how many items are displayed in a blog layout.
Change the number displayed in the LEADING field and be sure to click save.