Has to be a rounded down.Does anything in the LOTG or the FA rules requires the referee to play the exact or minimum amount of added time displayed by the 4O? I know the LOTG doesn't, Does the FA rules? Genuine question.
The time displayed can be a rough (rounded to the minute) indication of the amount of added time accumulated so far.
Law says the fourth official must show a minimum which can only be extended and not reduced. So if you show a minute, that's a minimum amount the referee must allow.
"The fourth official indicates the minimum additional time decided by the
referee at the end of the final minute of each half. The additional time may be
increased by the referee but not reduced."