I feel the need to add to this discussion. It may or may not have been said, but there is no direc need to dose 2 part in the exact same measurements all the time. it is two part because 1 is calcium and one is calcium carbonate (ALK). mixing hte two will cause the calcium to precipitate out of the solution so you have it in 2 parts.
you want to dose each bottle with what your tank is telling you per your tests. if your CA is low, add more of that to bring it up to respectable levels. same goes for the Alk. your corals may demand more of it from time to time.
I dont dose as i have a Calcium reactor on my system but recently since I was not testing often enough, my alkalinity was down in the 6's. I added just the Alkalinity supplement (BRS) over several days to bring it back up to 8.6 dKh. never touched my calcium since it was at 420.