I gave up a long time ago trying to figure out how they figure stars.
Here's what it says when I click "My Duke Starts" on the left nav:
Current Dukes You Have102
Total Dukes You've Earned in Sun Java Forums62
Total Dukes You've Awarded in Sun Java Forums10
Then when you click "Duke Stars Rewards Program Account Summary" on that page I get:
Duke Stars earned by program:
Sun Forum 122
Total Duke Stars earned to date122
Duke Stars spent to date-20
Available Balance 102
?
> there is a 49 duke difference. kinda odd isnt it?
Sometimes Sun gives you some extra. I have about 60 extra. Your Activity used to show where they came from now it only shows the last month. (I think 30 of mine was from when I created an account and another 30 was given to me at some point.)
> Duke Stars earned by program: 523
> Total Duke Stars earned to date: 523
> Duke Stars spent to date: -2
>
> vailable Balance: 521
>
> Where's my gold star? ;-)
It's based on this value Captain:
Total Dukes You've Earned in Sun Java Forums
You can find it by clicking on my duke stars, and it's the second line. They are only counting it based on the points you are given by other members, not by those points that are given to by sun when you run out/ do one of the tasks that gives you extra stars.