It is advisable that users bid their maximum amount that they’re willing to pay for an item, and let the system incrementally increase their bid, as necessary.
As the listing proceeds, the system will compare your bid to those of other bidders. When you have been outbid, the system will automatically bid on your behalf up to your maximum bid. The system will increase your bid by increments only as much as necessary to maintain your position as highest bidder. Your maximum bid reflects the amount you’re willing to pay for an item, but you could end up paying less.