Filemanager is unable to show actual file size for files > 4 GByte. If a file happens to be bigger the file size shown equals to the remainder of an euclidean division with the quotient equal to 4 GByte. Tested with Canon 650D, nightly build 2014-Oct-07. Cluster size doesn't matter. 32k cluster and 512k cluster Can be tested with cards <64 GByte. Just format the card with a cardreader and choose ExFAT instead of FAT.
Ciao Walter Schulz