Let's say that HarryCo, my own personal widget company, was IPOing. I'm selling 100 shares in the IPO.

Goldman Sachs would like to buy 50 shares for $14 each. Morgan Stanley would like to buy 50 shares for $15 each. Barclays would like to buy 50 shares for $16 each.

Citizen Bob would like to buy 5 shares for $24 each.

So what happens? HarryCo IPOs at $15 (the maximum I can get to cover all 100 shares) and then immediately pops to $24 when Bob buys 5 shares from Morgan Stanley.

I did not leave $900 "on the table" in my IPO because there wasn't enough demand to sell 100 shares at $24.