Ann: Drilling hits visible gold over 1km deep below Never Never, page-133

That adds another question, when are ounces actually proven?
Most mines have the majority of their reserve inventory in the probable category.
Value is such a subjective thing, when it comes to gold producers/developers, it's hard to compare assets using just one metric.
It's just a guide, nothing more nothing less.

Lucky for us, SPR's probability for success is continuing to improve as more value-add boxes are ticked off the list.