milliequivalent formula question

http://www.merck.com/mmpe/appendixes/ap1/ap1a.html

"The following can be used to convert between mEq, mg, and mmol:

mEq = mg/formula wt × valence = mmol × valence

mg = mEq × formula wt /valence = mmol × formula wt

mmol = mg/formula wt = mEq/valence

(Note: Formula wt = atomic or molecular wt.)"
So, for Sodium:
1 mEq = 23mg/23 (formula wt) x 1 (valence) = 1mmol x 1 (valence)
23mg = 1mEq x 23 (formula wt) /1 (valence) = 1mmol x 23 (formula wt)
1mmol = 23mg/23 (formula wt) = 1mEq/1 (valence)

Calcium has a formula weight of 40, and a valence of 2, so:
2 mEq = 40mg/40 (formula wt) x 2 (valence) = 1mmol x 2 (valence)
20mg = 1mEq x 40 (formula wt) /2 (valence) = 0.5mmol x 40 (formula wt)
1mmol = 40mg/40 (formula wt) = 1mEq/2 (valence)
40mg of Ca = 2 mEq
1mmol of Ca = 0.5 mEq
1 mEq of Ca = 20mg