A major pet peeve of mine is when people don't understand what "more" means in a mathematical sense.
I only buy double rolls of toilet paper. (You might think that those two sentences are unrelated, but you'd be wrong.) I figure it doesn't make sense, given the option, to not spend half as much time replacing rolls of toilet paper. They're just convenient. But Quilted Northern also lies on their packaging. On the front, they say that "12 double rolls = 24 regular rolls," which is true, and exactly what you'd expect "double roll" to mean. But, on the side, they say that a double roll has "2X more sheets" than a regular roll. That's a lie. If that were true, it would be called a triple roll, and it wouldn't fit in my wall anymore, so I wouldn't buy it. A double roll has 1X more sheets than a regular roll, or 2X as many as a regular roll—not 2X more.
I see this error all the time, and it makes me feel like the now-famous guy who had to explain to Verizon the difference between .002 cents and .002 dollars.
Currently listening: Quarashi—Dive In