Taking advantage of Apple’s (AAPL) relatively high (but not record) share price, the company’s senior vice president for iOS software — someone often mentioned as possible successor to Steve Jobs and Tim Cook — sold 64,151 shares at prices ranging from $601 to $605 to clear $38.7 million in one day. (SEC Form 4.)

The shares were the remains of a 120,000-share retention bonus that was granted in 2008, vested last month and reduced by 55,849 shares on March 24 to pay taxes. Forstall still holds 2,988 Apple shares worth, at Friday’s closing price, $1.8 million.

Although the sale represented 95% of Forstall’s current Apple holdings, that doesn’t mean he’s getting ready to leave the company. He has two more retention bonuses in the wings:

• 100,000 restricted stock units (RSUs) that were granted in 2010 and vest in 2014
• 150,000 RSUs granted in 2011 that vest in equal parts in 2013 and 2016, provided he stays with the company

Those RSUs, on top of Forstall’s $700,000 annual salary, are a powerful incentive to stick around. If Apple is headed to $1,000 per share within the next year, as some analysts suggest, Fostall could be looking at a windfall worth at least a quarter of a billion dollars.

That’s an awful lot of money.

But consider this: Forstall runs the software division that was responsible, between the iPhone and iPad, for $29 billion of Apple’s $39 billion total sales last quarter.

You can see why they might want him to stay.