Did you see the footnote?
- older flags were not recorded helpful/declined
The helpful/declined thing with flags is not there since time immemorial. You
quite obviously could have made some flags before the current system was set up. Flags from way back when have no records of helpful/declined, and so will never appear in either of the tallies.
Also, I am not exactly certain how comment flags are recorded as helpful/declined. Unlike post flags, moderators are not given the option to dismiss the flag while deeming it helpful. In particular, I think there are three things that can happen for comment flags:
- Enough users flag the particular comment and cause it to be deleted, or the comment is serious enough to warrant immediate moderator action (i.e. delete it or edit it) (things like profanity and such). In this case it will be helpful.
- Moderator dismisses the flag for whatever reason. In this case I believe it will be recorded as declined.
- Nobody does anything. Comment flags, unlike post flags which sit in the review queue until they are dealt with, expire after N days (I forgot what N is) if neither 1 nor 2 happened. Perhaps in this case the flag will be recorded as neither helpful nor declined? I don't know.