Gypsum Calc. Chloride Epsom Salt CaSO4 CaCl2 MgSO4 8.7 2.5 4.6 14.1 4.1 7.5 15 gallons sparge stop at 4.5 gallons
Based on boiling 14.50 gallonsliters at 1.049 for 100 minutes, this will decrease your wort by 1.67 gallonsliters, bringing your after boil OG to 1.055. You wanted an OG of 1.057. It looks like it will be under.