It is a bug which causes it to report the size of your entire Program Files folder rather than just the Quicktracks folder.
Download this registry fix to your desktop. Once the file is on the desktop, unzip it and place the file "Quicktracks Size Fix.reg" on your desktop. Double click the file. You will be prompted "Are you sure you want...", click Yes. You will then be provided with a confirmation, Click OK. This will resolve the misrepresented file size. Click Here to Download the file.
There is an update available for Quicktracks which resolves this problem for the future. There are some additional features as well.