Is this for your 14 gal
cube tank? I agree that dumping the block into the tank isn't the best way to go unless it's completely empty (no sand/rock). If it's just a bare glass/acrylic tank I'd add 1 cup and wait at least 4 hours to read the new sg
level. Make sure you have a ph running to mix it up.
If it's not a new empty tank then I'd mix about 2 cups (as best as you can measure a brick) in 2 gal
of water for at least 6 hours (with a ph) and top off your evaporated water with this solution till you get the sg
you want. (usually you use fresh to top off since salt doesn't evaporate)