The amount represents roughly 1.5% of his holdings.

Coinbase insiders and early investors sold about $5 billion in shares in total during the leading cryptocurrency exchange’s first day of trading on the Nasdaq earlier this week, according to series of filings made Friday with the U.S. Securities and Exchange Commission (SEC).

CEO Brian Armstrong sold 749,999 shares in three batches at prices ranging from $381 to $410.40 per for total proceeds of $291.8 million, according to one filing. While a Coinbase representative declined to comment due to the company being in a so-called "quiet period," based on filings made before the listing, it would indicate Armstrong sold about 1.5% of his stake.
In another SEC filing, it was disclosed that Coinbase director and venture capitalist Fred Wilson sold 4.70 million shares for proceeds of $1.82 billion. While it's not clear how much of Coinbase Wilson still holds, he's listed on the filing as a holder of at least 10% of the shares of Coinbase, which has a market cap of $63.6 billion.
Union Square Ventures, the VC firm led by Wilson, sold 4.70 million shares from its 2012 fund for proceeds of $1.82 billion, according to another filing. The fund is also listed as a 10% owner of Coinbase shares.
Together, the sales by Wilson and his firm's fund accounted for more than two-thirds of the $5 billion worth of shares sold.
Software engineer and venture capitalist Marc Andreessen, who is a Coinbase director as well as a holder of more than 10% of the exchange's shares, together with his firm Andreessen Horowitz and two associated entities sold a total of 1.18 million shares for $449.2 million, according to various filings (here, here, here and here).
An important thing to keep in mind is that selling by insiders was sort of the whole point of Coinbase's direct listing; it's from where the shares were supposed to come. The only thing new here is exactly who sold what and for how much. Unlike an initial public offering in which new shares are issued by the company with the proceeds going to its treasury, in a direct listing, the public is only offered existing shares that are held by insiders.
Even though a company gains no proceeds from a direct listing, it does benefit in other ways. In addition to allowing insiders to profit, a direct listing is a tremendous PR event and, more tangibly, vastly broadens the pool of holders while enabling the company to more easily raise capital in the future. As Noelle Acheson, CoinDesk's director of research, put it so well, "A direct listing is a liquidity event; an IPO is a capital-raising event."