Gypsum Calc. Chloride Epsom Salt CaSO4 CaCl2 MgSO4 11.2 3.2 6 13.0 3.7 7.0
Based on boiling 13.70 gallonsliters at 1.069 for 60 minutes, this will decrease your wort by 1.00 gallonsliters, bringing your after boil OG to 1.074. You were planning on an OG of 1.074 so you are right on track. Nice job!