array will look like after putting explicit bracings
arr[2,3,2] = {{{1,2},{3,4},{5,6}}, {{7,8},{9,10},{11,12}}}
a[1]-a[0] = 3 // no. of hops diffrence on 2-D array
a[1][0]-a[0][0] = 6 // no. of hops difference on 1-D array.
note: in both the cases intial and final position are same(i.e element 1 and element 7), but what matters is which type of hopping you are using 2-D hopping or 1-D hopping.