Piper Jaffray analyst Gene Munster said Monday that he expects Apple to turn in 2.7-2.8 million Mac unit sales during the current quarter, though he acknowledged that such prognostications are fraught with peril when most of the company's Mac sales traditionally happen in the month of September itself.

"With just one month of data," Mr. Munster wrote in a research note to clients covered by Fortune, "it is way too early to make a call on the quarter given ~50% of Mac sales in the quarter typically happen in the month of Sept."

Be that as it may, he said the company was on track to hit those numbers, which would represent a record September in terms of Mac unit sales. He also said Apple was on track to sell between 9.5 million and 10.5 million iPods during the quarter.

The September quarter is Apple's 4th fiscal quarter, and the company's performance during this quarter is often fueled by back-to-school sales.

Mr. Munster wrote that Mac unit sales were up 2% year-over-year in July, and according to his outlook this implies 3% to 7% growth for the quarter that ends in September. Wall Street is expecting 5% year-over-year gains for the quarter.

Shares in Apple fell more than 4% in trading Monday, part of a broader selloff. AAPL closed at US$159.59, a loss of $7.19 per share (-4.31%) on moderately strong volume of 18.7 million shares trading hands.

Each of the three major indexes also closed in the red, with tech shares leading the losses.

*In the interest of full disclosure, the author holds a small share in AAPL stock that was not an influence in the creation of this article.