That's a stretched interpretation. The first sentence says the interval does not exceed 15 minutes. The most natural way to read the last sentence is that the c

That's a stretched interpretation. The first sentence says the interval does not exceed 15 minutes. The most natural way to read the last sentence is that the competition rules state how long the half-time is under those parameters (i.e., the rules can state that the interval is 10 minutes, but not 1 hour); likewise, the referee can allow the competition organizers to change the duration of the interval -- the competition rules notwithstanding --, but still within the parameters of the 1st sentence.