How can I reduce the size of my virtual machine's file on my Macbook Air hard drive?

I'm new to Fusion, version 6. Yesterday I successfully downloaded the trial version to my Macbook Air and used the migration assistant to migrate my Windows 8.1 PC to my Macbook Air. It works great but the file size of the virtual machine on my Macbook Air is 200GB though the virtual machine's "Local Disk C:" says its only using 80GB of the 570GB available.

How can I shrink the virtual machine file down to something much smaller and is there a way to determine what an acceptable smaller size would be?

Thanks,

Stephen