How does it work?
There are a lot of bitcoins in the nutshell of Tumbler.cc. The bitcoins sent by customers go to the end of the reserve chain. After that the customer gets the same amount of bitcoins from the beginning of this chain.
The chain helps us to make transactions fast, as we don't need to wait for other customers' bitcoins.
How to use the mixing code.
The mixing code is created to eliminate the probability for a customer to receive his own bitcoins from a previous transaction.
Using mixing code you don't have a risk to receive your own bitcoins.