This attribute specifies the number of seconds that the Arbortext PE Request Manager will wait for an Arbortext PE sub-processes to terminate when the Arbortext PE Request Manager is ordered to terminate by the servlet container (for example, if Tomcat is shut down). The default value is 20 seconds.

You would not want to reduce this value. If it's too small, there might be an interval after Arbortext Publishing Engine termination when some Arbortext PE sub-processes remain running on the system.