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actually in most of methods like AES,DES have two important phenomena ,one is confusion and other is in whole process only Sbyte step bring confusion(brings non-linearity) while in diffusion data is just misplaced not changed.


To know how many boolean functions you got you have to look at the output of the S-Box... A $N \times M$ S-Box gives you $M$ functions. In the example you passed, you have a function $f_1$ given by $00 \rightarrow 0\\ 01 \rightarrow 1\\ 10 \rightarrow 0\\ 11 \rightarrow 1$ and a function $f_2$ given by $00 \rightarrow 1\\ 01 \rightarrow 1\\ 10 ...


Your n x n S-Box can be seen as a set of $ n $ boolean vectors of size $ n $. Actually you have got $ n $ functions, each one is the truth table of one particular vector (or column). In your example there are 2 columns thus 2 functions. For each column the number of 1's is 2.

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