all is in the correct way. The file has a size of 57 and it will be transmitted by the server :
id="0102" severity="info" sys="SecureWeb" sub="ftp" name="send file, clean" srcip="192.168.2.222" dstip="213.144.15.28" url="ftp://213.144.15.28/pub/ASG/v7/beta/asg-7.460-090618-4.iso.md5" user="anonymous" size="57"
but this depend on the security settings of the server. If the size is defined in the content length of the packet we can report it in the logfile. But some server don't deliver it in the content length and so the size is 0 in the logfile.