Um. That coffee recipe.
Let's compare it to Starbuck's black coffee. Which of the two is stronger?
More potent?
Actually depends on the grind itself, and the quality of the coffee beans.
Found a dark roast that was actually closer to light roast than was the norm, and found a light roast that would rip off your face and chase your pets.
Also, the caffiene content varies by roast and quality.
Discovered that different brands will yield wildly differing results.