Mail security for Exchange server Licenses

Hi There,

   Anyone can help me to explain what different about Symantec MAIL SECURITY FOR MS EXCHANGE ANTIVIRUS AND ANTISPAM 7.0 WIN 50 USERS BNDL STD LIC EXPRESS BAND S ESSENTIAL And Symantec MAIL SECURITY FOR MS EXCHANGE ANTIVIRUS AND ANTISPAM 7.0 WIN 50 USERS BNDL COMP UG LIC EXPRESS BAND S ESSENTIAL, since we need to buy 100 CALs of Antivirus and AntiSpam for a new Exchange server 2013 application for our new email server, however, don't understand what is different about this 2 licenses. Many thanks.