How WIRESHARK confirm the TCP OUT-OF-ORDER packet!

["李凌"<leering163 () 163 com>]

Hello,everyone!
        It is my pleasure to write here for you.
I've got some problems with the wireshark that how the software confirm if the tcp packet is out-of-order or not.
I captured a pcap file named 'example.pcap',in this file No.507, No.508 ,No.509 make me confused：
（because the pcap file is too large ，it is more than 7MB，so I have to export  the right packets as plain text named 
No507-No509.txt ）

507    IP_ID:15689    TCP_SEQ:727452     
        508    IP_ID:15690    TCP_SEQ:669373------out of order
        509    IP_ID:15691    TCP_SEQ:670825------TCP retransmission

No.508 Packet has a IP header ID that is 15690 which is bigger than No.507.This means the server sended No.508 packet 
after No.507 packet,and wireshark captured them the same way .So,as I known ,No.508 may be a retransmission instead of 
out-of-order packet.However, wireshark tags a out-of-order flag on No.508 which makes me confused,Is there any rule I 
don't get? I got nothing on the Internet about this question ，could you please help me？
Thanks a lot！
PS：Wireshark version 1.12.0 (v1.12.0-0-g4fab41a from master-1.12)
Best regards,
Ring Lee

Attachment: No507-No509.txt
Description:

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