As things stand all they can tell is that there is 1 bid on the item, unless they shill bid as mentioned above.
Had you bid 99p, then later gone back and increased your maximum bid then the seller would be able to see that there had be 2 “bids” but you were winning for 99p and from that could deduce that you have entered a higher maximum bid, but again would not know how much that was for.
I have sold stuff on ebay that I was certain would fetch a price and it has gone for 99p, and on the flip side I have also won items that I was certain were worth more. It’s a game, sometimes you win sometimes you lose, I wouldn’t withdraw a sale as it wasn’t for the price I was hoping for.