Actually, if you read my blurb again, I was admitting to the potential for 12 billion tons of NEPA anthracite reserves. I upped your reserves by 2 to 6 billion tons. I also said that perhaps only 60 million of those tons will prove to be "economically" recoverable.
Think of it like oil. In the mainland USA today at least half of the oil we started with is still under ground, but with many thousands more rigs (some big, many small) churning than in 1970 we can only annually pull out 50% of what we pulled out back then, and what we are pulling out is costing us a bunch more than it did back then. And in another generation or so we will be pulling less than 25% out of the 48 states than we did back in 1970, and it will not matter how many more straws we sink into the ground, as we will not reverse this terminally downward trend.
It's likely that at least half of the anthracite that was there before it was discovered is still under ground, but we highgraded it, and far and away most of the easy to get to stuff has already been mined, not to mention that some quantity was torched in place.