Count through 1 deck of cards, and if you do it right, your count will return to 0. count through another deck and once again, your count will return to 0. rinse and repeat.
this is exactly the same as 6 decks. After counting through every deck, your count will be back to 0, even if the decks have been shuffled.
This is because there is an equal amount of +1 and -1 cards. They will all eventually cancel out.
Good luck with your card games! and remember: practice makes perfect.

Get inside Andy's Bloch mind as he discover the secrets that made him Millions playing for the MIT Blackjack Team!
You will learn basic and advanced strategies, card counting, optimal betting and how to present your skills in the casino.