So in p.66 of Book II, Ansel Adams outlines his exposure formula:

Square root of your ASA give you the key stop
Take your meter reading in c/ft^2 (foot-candles) and the inverse is the shutter speed at the key stop.

So if shooting ASA100, the key stop would be f/10. And if luminance value is 100FC, then the exposure is 1/100.

I'm trying to get this to work with my Sekonic 758C. I'm not coming in close. At f/10 and 100FC with ASA 100, my exposure reading is 1/8 second. Even taking into account a K factor, this is orders of magnitudes off.
What am i doing wrong?