July 29 (Reuters) - Robinhood Markets Inc (HOOD.O) Chief Financial Officer Jason Warnick said he expects its $2.1 billion initial public offering (IPO) will demonstrate the benefits of allocating a significant chunk of stock to retail investors. The IPO valued the trading app at $31.8 billion, at the low end of its indicated range, and its shares are set to begin trading on the Nasdaq later on Thursday. The offering was notable for Robinhood"s decision to reserve between 20% and 35% of it for its users. "I think we"re well-positioned for this to be a successful demonstration," Warnick said in an interview, noting Robinhood would have one of the largest retail allocations ever on a U.S. IPO. The online brokerage has not yet disclosed how much of the IPO was bought by retail investors. Robinhood was contacting users last night to confirm their participation in the offering. Robinhood used its IPO Access platform to administer the offering to its users. The IPO of scrubs maker Figs Inc (FIGS.N) earlier this year was the first to become available to Robinhood users, and the app is seeking to secure allocations to more IPOs. read more Early indications on Thursday were that Robinhood shares were set to open slightly higher than the IPO price of $38. read more Many IPOs benefit from excluding retail investors, who end up fueling a first-day trading pop by snapping up shares in the open market. By letting many retail investors under the IPO tent, Robinhood is making it less likely that investors will see big gains on the first day. Robinhood has not instituted a lock-up for retail investors in the IPO but has said that those selling their IPO shares within 30 days of the listing may be prevented from participating in other IPOs through the app for 60 days.