There I was, all alone - in debugging hell.
Why was our GUI not able to display the required disk space that was needed? Why was it showing 0?!
And why did our unit tests of the FileManager all shine of vibrant green?!
I started deep in the mounts of what our prophets label the business layer -- it was correctly calculating the bytes based on the file sizes.
I continued upward towards the swamp-like territory of the GUI-people.
There I stood. Face to face, with...
int gb = (int)fileManager.RequiredDiskSpace / 1024 / 1024 / 1024;