Design-software company Figma’s stock rocketed 250% above its initial public offering price, and was headed for the largest ever first-day gain, after an IPO had raised more than $500 million.

Danny Rimer, partner at Index Ventures, led Figma’s seed round in 2013, when the company’s stock was valued at just 9 cents per share. He said he has long been impressed by co-founder Dylan Field’s product vision, and agreed with Field’s thesis that design is “the most important determinant” of many consumer-facing tech businesses.

Investors and bankers are wondering why the software company didn’t price its shares higher to capitalize on fervent demand.