Formated External Drive and a lot of space is taken up already?

Hi, I bought a WD 6TB external hard drive. It came formatted in FAT32 and I reformatted it to NTFS. After the format, I have 5.4TB available for use. Half a TB seems like a lot of space to lose, but I have read that some space must be taken up by some kind of system files or something, but that still seems like a lot to lose.