The Highest Building

Hi everyone!

I don’t understand why in this task at the first assert

assert highest_building([[0, 0, 1, 0], [1, 0, 1, 0], [1, 1, 1, 0], [1, 1, 1, 1]]) == [ 3, 4, ]

it gives the answer [3, 4]. Can you please explain why the answer [4, 4] is not correct?

Link to the task: https://py.checkio.org/en/mission/the-highest-building/