Where did my 'j' go?

I have a function that looks like

     float[,] LowerArrayBy (float[,] ar, float minValue){
         for (int i = 0; i < ar.GetLength(0) - 1; i ++) {
             for (int j = 0; j < ar.GetLength(1) - 1; j ++) {
                 ar[i,j] = ar[i,j] - minValue;
             }
         }
         return ar;
     }

I am creating an editor window and it currently runs without an error. When I attach MonoDeveloup and put a debug point in I realize that j is undefined.

why is that I am clearly stating (int j = 0 ; rest of for loop; j++)