I suggest you try searching your system. I guarantee you that you have a crapload of .dll, .inf, .ico, & numerous other files that are less than 64k.
I just did a search of my system & I have over 9,000 files that are 4k or less. If my FAT32 cluster was 64k (which it would be if I didn't customize), I would have 9000 x 60k = 540MB of slack space (at least).
Searching for files that are 63k or less, I have close to 15,000.
And none of that takes into account files that spill over into the next cluster...such as a 65k file using 128k of space on FAT32 partition with a 64k cluster size. Smaller clusters are more efficient.