SpaceX said on Monday that ​its underwriters had exercised the "greenshoe" option to purchase additional shares, increasing the total ​proceeds from its initial public offering to $85.7 billion from $75 billion that it raised last week.Elon Musk's rocket, AI and internet conglomerate, which sold 555.56 million shares at $135 apiece to raise the record $75 billion, became the ‌largest IPO in ⁠history ⁠even before the greenshoe option was exercised.The 'greenshoe' is a standard feature of most U.S. stock market listings that ​acts as a safety valve, helping underwriters support the stock and limit sharp price swings in the weeks ​after trading begins due to strong demand.SpaceX's shares surged 19% after the blockbuster Nasdaq debut on Friday.Reuters reported last week, citing sources, that the IPO had attracted more than $250 ​billion of investor orders, far exceeding the amount the ⁠company was seeking ‌to raise. The IPO was oversubscribed by roughly three-and-a-half to four ​times, underscoring the ​extraordinary demand for the offering.The debut, which analysts described as ⁠a "Goldilocks" stock market entry, hit the sweet spot of rewarding investors ​with a strong first-day gain, while avoiding the perception that the company ​had left significant money on the table by pricing the offering too conservatively.Its shares rose another 7% in early trading on Monday, adding to the strong gains recorded in Friday's historic market debut, which lifted the company's market capitalization above $2 trillion and made Musk the world's first trillionaire.Underwriters typically exercise the greenshoe option when a stock trades above ‌its IPO price. SpaceX said its underwriters purchased 83.3 million additional shares through the option.The greenshoe option is typically exercised in IPOs that have ​generated extraordinary ​demand from both Main ⁠Street and Wall Street investors."Demand significantly outstripped the initial supply. Retail interest was high, but several major funds submitted massive orders, so underwriters wanted to tap the overallotment to satisfy these massive ​positions," said Brian Jacobsen, chief economic strategist at Annex Wealth Management.The deal has shattered IPO records and become an early test of investor appetite for a new wave of mega-listings, with AI heavyweights Anthropic and OpenAI reportedly expected to follow it into the public markets later this year.Goldman Sachs and Morgan Stanley were the lead underwriters for the offering.