Any value is allowed, but the meaningful values are between 0 and 10. Increasing the value generates more log output. At XferLogLevel == 1 you should get one line of output per file, and it goes up from there.
If I'm trying to track down a problem, I usually start at 7.
You can also get addition log output from rsync_bpc (and rsync) using the --debug option. Run "rsync --debug=help" to see the options. There is one for ACLs, so add "--debug=ACL" to $Conf{RsyncArgsExtra}. Or you can add one or more -v options, eg: "-vvvv".
I'll reply to your earlier question about acls.
Craig