Don't bother, if it works great as you say, then everything is OK and your card has it's full 8GB capacity. The "problem" you experience is that in Windows you can see only the first partition on the SD card, which is formated in Fat32 and is 512MB in size. The rest resides on a second partition (created during installation) which you cannot see normally on a Windows machine.Check the size of your card in LE/Kodi, and you'll see the first and second partition and their size...
Checked and okay!
Confusing that you see only 1 partition in Windows.
Simple when you know this 
Thanks for the clear explanation and the quick response.