The gist was that we have have on O(1) counting system for small numbers and an O(n) system for larger numbers. It takes the same amount of time to count 3 apples as 5 apples cause you can just instantly perceive that magnitude. But it takes about twice as long to count 40 widgits than 20, cause you have to look at each one individually.
It seams reasonably that the threshold for the two systems would vary in different individuals.
In Rain Man, Raymond sees three groups of 82 toothpicks instantly. The waitress recognizes instantly that there are 4 toothpicks remaining - that's a much easier number to see instantly.
I believe that the ordinary maximum that people subitize is 4. I can believe that the threshold may vary between a normal 3-5 up to something as high as 10. And when playing fast-paced card games with friends, I think that my range is much lower and theirs may be much higher! But 82 is just unbelievable.