AS bids from 4 different locations to insure your bid makes it to eBay. Normally, bids 2 to 4 are rejected as 'to low', but occasionally bids arrive so close together eBay isn't finished processing one when the next arrives. When this happens, eBay ends up recording both. I've seen several auctions with 3 of the 4 bids recorded.
Not a problem, and you should not worry. Might make the seller and other bidders wonder how you did it though