"A quick calculation gives me an average of 1.75 M of 100% KCL over the area you describe. The final number (133 MT of KCL) is less but is, I think, mathmatically more accurate."
Either way, they can recover 3 MT/year for the next 40 years with only what they've found so far.
BTW: Great research. Just keeps confirming that we are all sitting on an awesome resource.