No, that is not much at all. One cannot really do much math with salt mixes since the amount of moisture in them is variable, but a half cup might make up a gallon of seawater, and adding that to 60 gallons only brings the salinity up a little, say from 1.0240 to 1.0244. 
The best way to raise salinity is to replace evaporated water with salt water, not by adding dry mix. To go from sg = 1.023 to 1.025, you'd add about 5 gallons of seawater to 60 gallons of tank water over however long that took.
The best way to raise salinity is to replace evaporated water with salt water, not by adding dry mix. To go from sg = 1.023 to 1.025, you'd add about 5 gallons of seawater to 60 gallons of tank water over however long that took.
