I am selling my car. People come to my garage one at a time and make bids to buy it. I make an immediate decision whether to accept or reject an offer after receiving it. I decide to reject the first N offers, mark the highest price P, and accept the first offer that is greater than P.

What value of N do you recommend to me if I expect that 270 people will make a bid?

If N is small, I can accept a small amount of money.
If N is large, I can reject the best offer.