Strange "Important" message is being displayed

I have an auction running with several bids. The auction ID is 24916127. At the very bottom, under the list of bidders, is this:

Important : Multiple items available. See more info links above in the "Bid" or "BuyNow" forms.

When I first saw it, I thought perhaps I had made a horrible mistake and listed a quantity of more than one (I only HAVE one), but it does show a quantity of one available (whew!)

I then went to an auction that I'm bidding on, and the message is there, too. And I can't find any "Bid" or "BuyNow" forms.

What does this Important message mean? And where would a buyer find the "Bid" and "BuyNow" forms? Could this be the reason a couple of people have "bought" something from me by mistake, by clicking on the BuyNow button when they didn't realize it would instantly become a purchase?