I'd be interested for you to cut-and-paste from J Crow's site where it says that one drop of 5% Lugol's has 18.75 mg.
In the meantime, this is what I've learned. Original Iodoral tablets have 12.5 mg (5 mg iodine + 7.5 mg iodide). Lugol's 5% has per drop 6.25 mg (2.5 mg iodine + 3.75 mg iodide). It takes 2 drops of Lugol's 5% to equal one original Iodoral tablet. (Iodoral also comes in a 50-mg size.)
It's easy in the beginning to get all the different formulas confused. I'd be happy to check out where you think Dr. Brownstein wrote that one drop of Lugol's equals one tablet of Iodoral, if you'd point me to the page and book he wrote it in.