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For many companies selling five million units of a new product the first weekend would be a blowout that could rally stock shares to new highs.

But not for Apple (AAPL).

The stock hit a record high Friday on expectations it would sell 8 to 10 million new iPhone 5 devices over the weekend. But Monday, after the company announced it sold roughly 5 million in the first three days of the launch, Apple shares fell 1% to $693.

Related: Apple's iPhone 5: Does It Live Up to the Hype?

Walter Walter Piecyk, tech analyst at BTIG, told The Daily Ticker, "Apple will have to do probably about 10 million to really excite investors."

Apple said demand for the new phone exceeded supply and the company sold out of its initial supply. Chief Executive Tim Cook said in a statement, "We appreciate everyone's patience and are working hard to build enough iPhone 5s for everyone."

The iPhone 5 launched in nine countries last Friday, and will debut in 22 more countries on Friday, September 29.

The next big number for Apple investors to watch, says Piecyk, is total iPhone sales in the December quarter.

"The whisper number appears to be around 50 million," says Piecyk. "There are a lot of analysts coming out at the high 40s. We're at 45 million right now.… If they don't put up 50 million or more they could be in trouble."

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iPhone sales are key to Apple's future as they account for more than 50% of Apple's revenues and more than 60% of its profits, says Piecyk. The key to future iPhone sales, says Piecyk, are sales in China, which could start before year-end, and carrier policies in the U.S.

Currently subsidies by Verizon Wireless (VZ) , AT&T (T) and other cellphone carries let users upgrade to a new smartphone for $200 instead of the $600 retail price. Customers can sometimes upgrade before the usual 2-year contract expires but that flexibility could end.

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Piecyk says those subsidies reduce carriers' margins because most customers now are not switching from feature phones to smart phones allowing carriers to collect an extra $30 a month for data but switching from one smart phone to another.

He says sales Apple could potentially boost iPhone sales if it introduced a new, lower-priced phone that could sell in Brazil, China, Mexico and other developing markets. Even with lower margin such phones could boost incremental profits, says Piecyk.

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