data[0] = 78 > 20 = data[14]

If i = 0 and j = 14 then data[i] <= data[j] is false, as data[i] = 78. Thus j - i is not to be considered.

If conversely i = 14 and j = 0 then data[i] <= data[j] is true. However j-i = 0-14 = -14 < 0, which means it is not the maximum.

(We are supposed to find the maximum j-i with data[i] <= data[j], not the maximum abs(j-i))

What do you want to be checked? I saw that you passed the kata... Furthermore asking for something is not an issue, sorry!