Lloyd, you are getting way outside my expertise. The 31% could be as you have supposed. The other possibility is the 31% may refer to a rate of return (IRR, MIRR, DCFROR) which would allow for the analysis of processing/mining costs and expected product prices. I can make a guess this is not a shovel full estimate, but is possibly based on core drilling and geological analysis. Since I do not do any hard rock mining in my investments, this is just speculation. See if you can find someone at UNR’s mining department to point you to better reference information and possibly some good teaching videos.