Resolution:
The value of the Acceptor Thread depends on the use of a Non-Blocking I/O socket or a Blocking I/O Socket. The user can specify a Blocking or Non-Blocking I/O Socket in the HTTP Connector Resource Template -> Advanced -> Use Non-Blocking IO Sockets option. By default, "Use Non-Blocking IO Sockets" is selected with a non-blocking socket and only one Acceptor thread will be able to execute an "accept" since "accept is a synchronized method for a non-blocking socket. This is the reason the default value of the Acceptor thread is set to 1 and non editable. If you use the Blocking I/O Socket, the default value of the Acceptor thread will be changed to 20 and will be editable.