Yeah, I would dose calcium to bring it up by 50ppm per day. I just did this with my tank when I saw my calcium was only 300. I used calcium chloride and J Dieck's reef calculator:
http://reef.diesyst.com/chemcalc/chem_calc3.html
I would think that Nook means to manually dose to get your Ca up and then test to make sure that your Reactor is keeping up with the demand.
From the calculator (based on 130 gallons water volume):
Calcium chloride dihydrate:
162.5 grams; 5.7 oz; approx 32.5 tsp
Balanced alkalinity:
4.45 meq/l at 450 ppm
Warnings and usage:
Dissolve it in RO/DI or distilled water before dosing and not dose all at once. Although it may be ok to do so, I don't recommend it. Dose 1/3 to 1/2 and the next day test. Check your levels and then dose another portion.
Nice tank! Do you have the tall pile of rock on the right side of the tank secured together or just stacked up?
Looks good.