Close OPC UA Server session|OPC UA Standard|Forum|OPC Foundation

I have developed OPC UA SERVER application using CSharp(C#) language.

My requirement is:

OPCUA server shall close an established TCP connection when OPC UA client is seen as inactive during a configurable period time.

I have configured the server session timeout in OPC UA Server config file (60 sec)

<MinSessionTimeout>1000</MinSessionTimeout>
<MaxSessionTimeout>60000</MaxSessionTimeout>

But when I disconnect the server from client, the session is closing immediately. it is not waiting till 1 minute.

How to handle it?