Today’s IPO of trendy burger chain Shake Shack attracted as much attention as it did money. Shares opened at $47, vs. the IPO price of $21 per share. That’s a huge jump, and far more dramatic than the one consumers are likely to see in the company’s U.S. footprint in the near term. The chain of 63 restaurants—roughly half of which are in the U.S.—plans to open just 10 or more domestic stores per year to a target of more than 450 U.S. locations, by a date it has yet to specify.