Explanation :
Size of the jacobian matrix is,
$ 2\;\mathrm m-\mathrm m-1\times2\;\mathrm n-\mathrm m-1 $
Given that 10 generator buses, we need to assume with in the 10 buses one bus as slack bus then,
$ \left(2\times100-10-1\right)\times\left(2\times100-10-1\right)=189\times189 $