If the packet of US05 was fairly fresh, then you should be fine. MrMalty.com yeast starter calculator for dry yeast with OG of 1.062 and a 5 gallon batch, suggests 1 package of yeast (the 11.5 gram size) if yeast was new. Even if 6 month old yeast, it suggests only 1.2 packages, so sit back and wait for it to take off!
If you were using liquid yeast you would definitely have needed 2 packs/vials or more without a starter, but dry yeast has more yeast cells then liquid.
Member of the Metro South Homebrew League (Mash-Holes) - Weymouth, MA
Primary - Peter Piper's Pale of Pumpkin
Secondary - Azacca Pale Ale
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