Billionaire hedge fund manager Bill Ackman, founder of Pershing Square Capital Management, made a big bet earlier this year on "Magnificent Seven" stock Microsoft (MSFT +1.92%). In the first-quarter 13F filing, released in May, Pershing Square revealed it bought 5.7 million shares of Microsoft stock at a value of $2.1 billion. The purchase came when Microsoft stock was trading at a price-to-earnings (P/E) ratio of 21, the lowest it had been since 2017 and some 32% below Microsoft's average P/E ratio of 31. Microsoft stock goes parabolicSince Microsoft reported earnings on July 29, its stock has gone parabolic, as I predicted a few weeks ago. As of the end of June, Microsoft stock had been down about 23% year to date, trading at around $373 per share.