Greetings from Vienna, I'm a new member!

I have a bit of trouble with this tutorial from Line25. After downloading the icons, I must select four of them in order to build this menu:

According to CSS, each square is 120 x 120 px. And this is what I achieved putting one of those icons into a 120 px square:

As you can see, quite smaller than the original. The author of the tutorial did not use Illustrator to assemble the four icons but Photoshop, so he couldn't enlarge them.

What did I wrong? Thanks in advance.