"Players are entitled to an interval at half-time, not exceeding 15 minutes; a short drinks break (which should not exceed one minute) is permitted at the interval of half-time in extra time. Competition rules must state the duration of the half-time interval and it may be altered only with the referee’s permission."
My interpretation is it is 15 minutes unless the referee allows something else.
alt Hacker News
"Players are entitled to an interval at half-time, not exceeding 15 minutes; a short drinks break (which should not exceed one minute) is permitted at the interval of half-time in extra time. Competition rules must state the duration of the half-time interval and it may be altered only with the referee’s permission."
My interpretation is it is 15 minutes unless the referee allows something else.