I don't understand either.
Bulletin 1
Critical
Remote Code Execution
May require restart
Microsoft Office, Microsoft Office Services and Microsoft Office Web Apps
Bulletin 2
Critical
Remote Code Execution
Requires restart
Microsoft Windows and Internet Explorer
Bulletin 3
Important
Remote Code Execution
Requires restart
Microsoft Windows
Bulletin 4
Important
Remote Code Execution
May require restart
Microsoft Office
Also the April edition of the Malicious Software Removal Tool will be available for download next week.
Also this is the final set of updates for Windows XP. Technical support for XP will be ending with this set of updates.
More information regarding the ending of Microsoft support for Windows XP is provided here,