Ann: Operational Update - Significant Progress on all Fronts-88E.AX, page-109

I think the IRR is valid, but it does come with a few limitations, which are certainly clear to DeMac as well as the market.

Their report is very thorough, but it does fall short simply because of the industry reference used. It is clearly the only way the report can be constructed at this time and hence the lower number. Not against PB's as such, but a lower number compared to the more likely reality of the yet to be confirmed "unique play".
It's a little more complex than at first glance.

PB is clearly being very restrained in his estimate funnily enough, as he follows the Demac model closely, other than the acreage and slightly different RF. What is interesting is that IF his model proves up and the oil in HRZ is in fact in a vapour phase across the acreage, then the RF will be revised up enormously, as will the flow rate (Ice 2H to prove). We may soon see a new estimate referenced to the 2D/3D and core characteristic updates in a few weeks. All will effect BE and total resource estimate. The key here being an improved RF, which could affect the overall resource estimate "significantly" (hint).

What is interesting though is the consistency between DeMac and PB's analysis. The probability and resource estimate equations are all very standard and are accepted industry wide. The difference in the two is quite obvious. I don't believe the DeMac number is invalid, but you probably need to look at its derivation in more detail, where you will see it's limitations laid out for all to see.