rsync counts not identical

[David Mehler]

Hello,

I'm using rsync on two FreeBSD servers to send files and subfolders
from one to the other. The command I'm using is rsync -avz
/path/of/first/system/folder/ /path/of/second/system/folder/

The first set of files/folders is on a ufs disk, the second on a zfs
volume, differences in sizes are 13 to 20MB differences between the
source and destination. Is this normal?

Thanks.
Dave.