PowerShares QQQ (NasdaqGM: QQQ) was in the red Monday after top holding Apple (NasdaqGS: AAPL) said it sold more than 5 million iPhone 5 units over the weekend, which came in below bullish analyst forecasts.

Apple shares were down 1.4% in afternoon dealings while the Nasdaq-100 ETF slipped 0.5%.

Apple dominates QQQ at 20.3% of the ETF’s portfolio. The next-largest holding is Microsoft (NasdaqGS: MSFT) at 8.1% of the tech-heavy fund, which is one of the largest and most highly traded ETFs.

Demand for iPhone 5 exceeded the initial supply and while the majority of pre-orders have been shipped to customers, many are scheduled to be shipped in October, Apple said in a press release Monday.

“Demand for iPhone 5 has been incredible and we are working hard to get an iPhone 5 into the hands of every customer who wants one as quickly as possible,” said Tim Cook, Apple’s CEO, in a statement. “While we have sold out of our initial supply, stores continue to receive iPhone 5 shipments regularly and customers can continue to order online and receive an estimated delivery date. We appreciate everyone’s patience and are working hard to build enough iPhone 5s for everyone.”

Apple shares dropped back below $700 after rising to an all-time high on Friday.

Some Wall Street analysts downplayed the company missing optimistic iPhone 5 sales projections.

“To us, it isn’t about how well a product does in a few days but how it does over the next 2-4 quarters,” said Shaw Wu of Sterne Agee in a MarketWatch report. “We continue to believe iPhone 5 is a significant update and will drive a powerful product cycle.”

“We believe that if supply were not a constraint and Apple included all pre-orders, the launch weekend number would have been closer to 7-8 million, assuming ~1 million October pre-order sales and an additional 1-2 million units at retail,” added Gene Munster of Piper Jaffray in the article.

“We believe that sales could have potentially been much higher if not for supply constraints,” William Power, an analyst with Baird Equity Research, said in a Reuters report.

“Expectations for Apple are always white hot,” said Colin Gillis, a research analyst with BGC, in the story. “It’s not just enough for them to break records but to smash them.”

Apple shares were up 73.5% year to date heading into Monday’s trading, according to Morningstar. QQQ, the Nasdaq-100 ETF, was up 26.5%.

PowerShares QQQ

Full disclosure: Tom Lydon’s clients own QQQ and AAPL.