wrong file size in the download log?!

[Carlos Carvalho]

I use %l in --out-format to have the file size in the download log.
However for some files what rsync puts in the log is different from
the real size. Sometimes it's larger, sometimes smaller. It happens
with the latest v3.1 in the destination and 3.0.6 in the
origin/sender. The md5sum reported by rsync (from %C) matches the
contents on the destination disk. There are no error messages for
these files.

How can the size reported by rsync be different from the real one??

Does rsync put what the receiver writes in the log (as I think it
should) or it just puts the number the sender tells? If so, the number
can be wrong if the file changes in the origin during the transfer.