Though only 10 achievements are available as from today, all which can be unlocked via the Legendary Maps and the Campaign mode, Bungie say that it will also be adding another 500 points worth of achievements over the coming weeks.
The complete list will then contain 79 achievements, totalling 1750 points.
We thought Microsoft's official Gamerscore policy was that developers were only allowed to offer 1250 Gamerscore points max - 1000 points unlockable for free and 250 points for extra downloadable content.
Seems that Halo 3 is an exception to the rule then, unless Microsoft has amended its policy?
We've been doing some snooping around, but can't seem to find a new policy on Gamerscore points. We've contacted Microsoft and are awaiting clarification.
The full list of achievements can be found at Console Monster