Hey Edward,
By front page, are you referring to the '/blog' page? If that's the case, for the magazine menu item, unfortunately you can only display up to 9 posts on the page(
http://take.ms/Fz1DA), which is 3 x 3.
For grid menu item, you can manually select the number of posts to display on the page(
http://take.ms/HRKfO).