Comparing their JORC target to what they actually found, it...

Comparing their JORC target to what they actually found, it seems their coal tonnage is 10Mt for each metre of coal thickness over the 7.2 sq km area they have identified as prospective.

So if the average coal thickness is 50m, target is 500Mt. If it's 80m, 800Mt. And so on.

Obviously these are only rough figures and they won't JORC it all at once, so don't expect a 1 billion JORC straight up. Also keep in mind the deposit appears to dip at about 30 degrees which means the true thickness is going to be less than the intersected thickness (about 15% less). Finally, there will probably be a depth cutoff depending on who does the JORC estimate.