That is simple. When you make the match, you stop at Nth catd, while N+Cardvalue is always equal to eleven. So, if you make the match, instead of putting all the cards on the pile you just put them away in the final round. So, you are on the count 33 as you never put the last card away but reveal it. 52-33 = ? Behold, it works!
The deal is that the cards number directs you to the 9th card always, thats what makes it amazing and you will never figure it out, i know this trick long time ago and i thought in every solution but i couldnt :/ its pure math or statistics i dont know!!!
The only time it doesn't work is if you don't have any matches, in that case you turn over the last capped card which will reveal their card. If you aren't getting it any other time, you're doing something wrong.
I can't belive I did it on my first go
Yay