Portee,

If you're having trouble doing this stuff in your head, then like the constipated accountant who couldn't budget, maybe you could work it out with a pencil.

Seriously, I think 25 times background is not exceptional. Most results I have seen have been as %U308, not simply scintillation readings indicating anomalous radioactivity. It certainly indicates that something is there, but it's not the motherlode. Seems to be a theme with KXL.

Meanwhile, here's an oldie but goodie to while away the time until the next NR:

Mining and refining gold