Why does the Disk Utility show different amount's of space used?

Hey everyone,

I have a 2014 Macbook Air with 120GB of space and OS X El Capitan. Disk Utility say's i have used 27.96GB but the divided bar graph above say's i have used around 44GB of space. Why is this?

As you can see Disk Utility state's i have used 27.96 but above that in the divided bar graph it say's i have used over 40GB of apps. How is this possible? I certainly don't have 40GB worth of apps!