Comment 4 for bug 1066012

man rsync:
"A p means the permissions are different and are being updated to the sender’s value (requires --perms)."

For compatibility with different filesystems and lot other things BackInTime stores permission of files in an additional file (fileinfo.bz) and change permissions of files and folders . They are owned by the user running the backup and only readable.

If you want to compare the files manually you'd have to add at least '--no-p --no-g --no-o' to your rsync command to avoid detecting this difference. You should take a look at the log which arguments BackInTime use for rsync and adept these to your own dry-run.

Regards
Germar