How did this happen?

I just sniped a Missoni dress - opening bid was $175 and there was a reserve. Auction sniper placed the bid and even though I was the only bidder it jumped up to $280 (which I'm guess was where the reserve was set but I don't know) and I won. Is this a new Ebay thing? I'm psyched that I won but completely confused.
 
Yes, if the reserve was set at $200, and you bid $250 and the current bid is $10 then when you place your bid it will go from $10 to $200 even if you aren't bidding against anyone else.
 
Yes I put my max in at 300 I've just never seen that happen before... I guess the few times I've bid on auctions and the reserve wasn't met my max bid was still lower then the reserve price.

Thanks for clearing up my confusion!