Use this calculator:
http://reef.diesyst.com/chemcalc/chemcalc.html
For the calcium part (Reef Foundation A):
select the entry for Randy's Recipe #1
multiply the amount needed by 0.185 (that is, you use about 5x less)
For the alkalinity part (Reef Foundation B):
select the entry for Randy's Recipe #1
multiply the amount needed by 0.53 (that is, you use about half as much)
For the magnesium part (Reef Foundation C):
select the entry for Randy's Recipe
multiply the amount needed by 0.48 (that is, you use about half as much)
This all assumes the info on theior web site, such as:
"Liquid supplement: 1ml will raise the Ca level of 100 liters (25 gal) by 2ppm."
is correct.