You have gone through the process of successfully authorising your licences, the number of licences has increased but the old expiry date is still being shown in the 'Availability' tab (see below). The likelihood is that you actually have authorised your new licences which will expire with the new expiry date but you are stiil seeing the old licence date as they has not been deauthorised. To check, double click on the licence within the ‘Availability’ tab in the ArcGIS Licence Server Administrator.
This will open up a new window and you will be able to see both licences; your new ones and your old ones, check the expiry date to ensure this is the case.
If you want the ArcGIS Licence Server Administrator to show the new expiry date then you can selectively deauthorise the old licences, the knowledge base article here explains how to do this. However, you do not have to do this, the new licences are ready and in place to take over from the old licences. Once the old licences expire they will automatically roll over to the new licences and display the new expiry date in the 'Availibility' tab.