question about deletion and counts

[Jeff Templon]

simeto:~> notmuch search --output=files tag:deleted | wc -l
     666
simeto:~> notmuch search --format=text0 --output=files tag:deleted | xargs -0 rm

afterwards, from notmuch new:

No new mail. Removed 577 messages. Detected 89 file renames.

577 + 89 = 666 ... my guess is that there were 577 messages and 89 files
that represented duplicates of messages.  But I didn't rename the files,
I deleted them.  Should I worry?  Why is the message inaccurate?

JT