If you've been watching Nordstrom's (NYSE:JWN) shares fall by almost 5% since the company reported July's same-store sales last Thursday morning, you might assume that the comps numbers were terrible. Well, just remember what happens when you assume.

Nordstrom's comps for July actually rose 9.4%. So what's the problem? Well, a calendar shift meant that July began and ended a week later this fiscal year, but it also added an extra week to the period. And although that additional week boosted sales, management said it negatively affected the quarter as a whole. The exact impact wasn't quantified, but same-store sales still would have risen 5.9%, which in turn still trounced Wall Street's 4.2% expectation.

Some onlookers also may have been spooked by projections for a comparatively sluggish fourth quarter, which is an important selling period for all retailers. And just to make things more convoluted, the third quarter will see a gain over last year, while Q4 will come in lower. In tandem with that performance, the company expects a 4%-5% increase in same-store sales for the next quarter, and a smaller 2%-3% rise in the following period. But for the year, when all of the calendar shifts are balanced out and their impact is removed, same-store sales should still increase by a solid 5%-6%.

Nordstrom remains the class of the luxury retailers. Its legendary customer service is a competitive advantage that can't be easily duplicated, and the company spends a lot of time, money, and effort training employees to maintain that distinction. For instance, on its website, you can get live help not just from a customer-service representative, but also from a beauty consultant and a designer specialist. While Saks (NYSE:SKS) is improving in this area -- and reporting very good same-store-sales results -- it is not at Nordstrom's level just yet.

At a trailing price-to-earnings ratio of 18, this just may be one stock to grab before the sale is over.

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Fool contributor Larry Rothman is happy to receive feedback, and he promises to read it when he's not being wrestled by his three children. Feel free to email him at rothmanviews@comcast.net. He doesn't have any positions in the companies mentioned. The Fool has a disclosure policy.