TCP time wait error

Hello, everyone. I"d like to ask about the time waiting error of the TCP protocol.
TCPIP description: when the FIN exchange is completed, the next serial number of the client is K, and the next serial number of the server is L. the recently arrived message segment is sent to the client by the server. It uses the serial number Lmur100 and contains the serial number KMui 200. After receiving it, the client thinks that it has received the old message segment and sends an ACK, containing the latest serial number K, L. after the server receives this message segment, does not have any information about the connection , so it sends a reset message segment.

how to understand the bold part,

Tcp
Apr.11,2021

because the state of the connection on the server is already closed, all resources of the connection are released, that is, there is no information about the connection

.
Menu