mass delete

I just wanted to make sure if these options are correct! I have replaced -1 with 0 in the second field of message count and entered a time period till one year ago. I wanted to confirm because the number I am getting through this search is pretty large. It is probably accurate as I suppose...

Recently I just set a signature limit on our forums. It works for people that haven't created a signature yet. But people that had a signature before hand haven't gotten there signatures limited until they edit their previous one. Is there a way I can mass delete everyone's signature?