Edit distance (Levenshtein-Distance) algorithm explanation

Question

I want to calculate the edit distance (aka Levenshtein-Distance) between two words: «solo» and «oslo».

According to this site we'll get the result matrix:

What I don't understand is: In case of comparison the last «o» from «solo» with the first «o» of «oslo» will see the submatrix:

3 2
4 3

As far as I understand, in order to calculate the bottom right value, which is equal in this example to 3 of this submatrix, we'll get the min(3, 2, 4) + (0 if the letters are the same, otherwise 1). So, why in this example the bottom right value is equal to 3 and not to 2?