Because in our sample of 40 days, the Hob has had fewer than 20 customers 25/40=5/8 of the time, the best estimate of the probability that there will be fewer than 20 customers the next day is 5/8. If the Hob had fewer than 20 customers 5/8 of the days, then it had at least 20 customers 3/8 of the days, so the best estimate of the probability that it has at least 20 customers the next day is 3/8.