The thread index. It contains one line per subject, starting with the
number of the first message with that subject within the set
investigated, ``:'', a 20 character
-subject hash, blank, ``\[n\]'' where ``n'' is the number of messages in the
+subject hash, blank, ``[n]'' where ``n'' is the number of messages in the
thread, blank, and the subject.
The file ``yyyymm'' contains
entries for all threads that have messages in the month ``yyyymm''