No errors found, or successfully repaired.
https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man8/fsck_hfs.8.html
» EXIT VALUES
» fsck_hfs indicates some status by exit value. The current list of exit status results is:
» 0 No errors found, or successfully repaired.
» EXIT VALUES
» fsck_hfs indicates some status by exit value. The current list of exit status results is:
» 0 No errors found, or successfully repaired.