I think someone is mixing up resource and reserve, resource is...

I think someone is mixing up resource and reserve, resource is the estimate to date of the entire body of gold, the reserve being a subset of that which is economically recoverable.

Its like having gold coins on the bottom of the ocean. The entirely of all the gold coins that you either know about, or can make a strong inference about the existence of, is the resource. However some will be so far spread out, or in such a depth of water as to be uneconomic to recover.
The ones that can be recovered economically, because they are grouped together and/or in shallower water are the reserve and it is the estimate of that which is the important bit.

Of the 3.05Moz resource, AUC are suggesting that currently is 1.28M oz is economically recoverable.