Single, Double, and Triple Stacks?

I've heard pills being called singles, double stacks, and triple stacks, but on these forums a lot of people say it's just nonsense. But today I did see three pills, all Blue Runningmen, and they were different sizes. The singles were curved on the top and bottom surfaces, and the doubles and triples were flat. And the triple was bigger than the double, for sure. Any input?

 

i agree i seen a single peach butterfly in florida and some double blue dolphins at home im curious about this as well

 

Were they all from the same dealer, or from various sources? Often times when rival manufacturers mimic prints, there are differences in the shape of the face and/or size of the pill due to variations in presses...