Unlike a company stock, the number of shares outstanding of an ETF can change daily because of the continuous creation of new shares and the redemption of existing shares. (fidelity.com)
At today's share price, this would reduce shares outstanding by 19 %. (ammdividendletter.com)
That allows it to book the reduction in shares outstanding immediately, and the bank then buys the shares on the open market over the ensuing months. (reuters.com)