It varies pretty widely, but Levie's number is on the low side historically for tech companies, particularly for such a relatively young company.
Gates had 45% of Microsoft the day after their IPO. Larry Ellison still owns ~20% of Oracle. Google's founders still have ~10%. David Filo even still has around 9% of Yahoo (Yang & Filo had closer to 20% at the time of the IPO if I recall). Bezos still has around 18% of Amazon. When Dell IPO'd, Michael Dell still owned a huge percentage of the company at IPO, over 40% if I recall (he sold most of it high, which is why before they took Dell private, he was nearly worth more than the company).
Gates had 45% of Microsoft the day after their IPO. Larry Ellison still owns ~20% of Oracle. Google's founders still have ~10%. David Filo even still has around 9% of Yahoo (Yang & Filo had closer to 20% at the time of the IPO if I recall). Bezos still has around 18% of Amazon. When Dell IPO'd, Michael Dell still owned a huge percentage of the company at IPO, over 40% if I recall (he sold most of it high, which is why before they took Dell private, he was nearly worth more than the company).