The organizer called on visitors to come within the time period stated on their reservation tickets。
组织方呼吁参观者按照预约券上指定的时间按时参观。
句中的reservation ticket就是预约券的意思。ticket除了表示“车票、门票”,还有“罚单”的意思,如:He got a ticket for speeding。他因为超速而收到罚单。ticket也可以做动词,给……开罚单:The policeman ticketed the drunk driver。警察给醉酒驾车的司机开了罚单。