Session not timed out as per configuration in Admin Console

Hello,

In Admin Console, we have configured "Idle Session Timeout" as 20 minutes . The users authenticate using SAML via SSO login. However, we observed that the session is not timed out in 20 mins always. If we open multiple tabs, certain tabs are timed out whereas few are still logged in after 20 mins.

Is there any reason or configuration change which needs to be done?

Thanks in advance..