Why does my empty SD card not have full capacity?

[elmoreas]

It is a San Disk 8gb SD HC SD card and it is formatted to NT FS, slow way. Under properties it shows that it has 7,960,756,224 bytes capacity and 32,768 bytes used but only 7.41Gb Free space. I know the drivers cannot take up that much space if they are on there at all after a format and I have checked for hidden files so what is taking up this space and why is it like this on all the cards I own regardless of mfg and format? This is something I have wanted to know for a while so if anyone knows I would appreciate some insight. Plus if it is possible to get the space back info on that would be nice as well. Thanks and have a good day. -elmoreas