How do I know if my SGS2 is up to date?

I clicked "check for updates" and said I was up to date.

In my "About Phone" it says:

Model: GT-I9100
Android: 2.3.3
Baseband: I9100XXKDH
Build: GINGERBREAD.XWKDD

Is this all upto date or should I be updating the software from somewhere?