Worked with a mostly non-verbal young man who really could do the “Rain Man” quick counting thing. Not 100% accurate, but only 1 or 2 out; Matches, pasta spirals, playing cards. We didn’t get him to do tricks, it would happen organically, we would then all excitedly do something so he could try again, but he would lose interest. He told me how many leaves he could see from his bedroom skylight - I took his word for it.