No, instructions are not wrong, and tests are not wrong.

You are experiencing problems caused by the fact that your solution uses an approach which loses some precision at some step. You need to find a way to keep your calculations exact so intermediate or final numbers do not get incorrectly rounded or truncated. There's hint in the description to stay in domain of integers all the time.

Avoid real division, avoid floating point inaccuracies, and avoid unnecessary rounding, and things will be OK.

Please say which language you're using. I have solved this kata in several of them and had no problem with that, seconds must be rounded down.