What does the #TCPTXDELAY: 100 command mean?

The #TCPTXDELAY command determines the time delay before sending a TCP frame that has not been entirely filled with user data.

The time is in milleseconds and the default is 100 ms. If you set 0 then it initiates sending a TCP frame as soon as it receives a character from the host. This command affects the FTP services and the TCP services.