If you have more than one of the same item to sell, then this auction is known as a Dutch auction. The seller needs to specify the exact quantity of items available to sell to either one or more bidders.
Dutch auctions (or multi-quantity auctions) have slightly different rules than regular auctions. In a Dutch auction, a bidder can bid for the quantity of items they would like to buy, their bid amount is per item.
When you see a quantity of two or more on any auction, that's a Multiple Item Auction (Dutch Auction). This means the seller is offering multiple, identical items for sale. Unlike a regular auction, Multiple Item Auctions can have many winners.
When you bid on a Multiple Item Auction, you specify the number of items you're interested in and the price you're willing to pay. All winning bidders will pay the same price, the lowest successful bid.
Much of the time, all buyers pay the starting price in Multiple Item Auctions. However, if there are more bids than items, the items will go to earliest successful bids.
To beat another bid, yours must have a higher total bid value (bid price x number of items bid on) than other bids.
You have the right to refuse partial quantities. This means, for example, that if you bid for 5 items and are offered only 4 when the auction ends, you don't have to buy any of them.