When downloading a big file from the server, initially the info in the list column of wireshark sound reasonable. However, as the downloading process ends(using totally about 60 secs), the time stamp in wireshark console just passed 30 secs. And in the next 60-30=30 secs, only "TCP segment of a reassembled PDU" is shown in the list column, while the detail info of each these packets are still reasonable.