NAD+ Concentration conversion

One maker of a NAD+ booster is claiming their trial was a success based on seeing a 17 ng/ml increase in intracellular NAD+.   But they did not provide baseline or control NAD+ levels.    From one tester of NAD+ levels a good level would be about 50 micromolar (50 micromol/L)

My conversion

660 grams/mole for NAD+ 50 micromolar is 0.00005 mole/L

0.00005 mole/L x 660 gms/mole = 0.033 gm/L

1,000,000,000 ng/gm x 0.033 gm/L = 33,000,000 ng/L

1000 ml/L 33,000,000 ng/L x 1L/1000ml = 33,000 ng/ml

17 ng/ml is trivial compared to 33,000 ng/ml but not 100% sure my conversion is correct.    Would appreciate a check by anyone competent in chemistry conversions.