I had ~20 flags declined, and I do not know why. In addition, I posted to the "Ask a SU mod" chatroom why and did not hear back (hence me posting here).

Why were these flags declined?

EDIT: As a response to Diago's answer (now gone, not sure why) I would say a few things:

1. I appreciate the fact that you don't want to deal with a lot of flags all at once, and in some small sense, I am sorry for that.
2. That is NOT however, a reason to just mark the flags as invalid. I do not exactly know how mods deal with flags, but I believe that it is possible to not review the flags in order. As mentioned by someone (I think @Breakthrough) if you don't have time/patience to review the flags, then don't, but that is a terrible reason to mark them as invalid.
3. To echo @Daniel Beck and I believe others (Breakthrough as well?) I acted with the best of intentions (as evidenced to some extent by my 700+ flag weight before this), in accordance with many meta posts, and made it clear, in act (this was not the first time I flagged so many things) and in word (I made a post asking for more flags) that this is what I was going to do to a greater or lesser extent.
4. Finally, to quote someone else (don't remember who, apologies) it is not possible to spam flags. I don't think that the issue is that the flags were bad. I think (and I think that most people agree with me) that a valid flag should get marked as such no matter how many there are in the queue.