Hey Eardan and others: in short, it worked!
I applied the appropriate math as follows. For 100ppm:
875000000 / 10 000 000 * (10,000,100 - 10,000,000) = 8750
Using the uBitx manager, My Master Calibration was already set to 138,250. So I subtracted 8750 for a total of 129,500.
I noticed that I was sill not quite dead on with WWV. I repeated the measurement and math and ended up with 127,458 for my master calibration value.
Thank you very much! I am much more on frequency now.