Since there is no uniform definition of "full liquid" or "water discount," I believe it helps to refer to lye concentration instead.
Remember that NaOH only needs an equal amount of water (by weight) to dissolve; this would be a 50% lye concentration. Unless you are using a very high lye concentration (close to 50%), or a very concentrated sugar solution as your entire water amount (or both), you should have more than enough water left in the recipe to dissolve the NaOH in your sugar solution.
But if not, you will see undissolved particles in your mixed NaOH-sugar solution. In that case, add small amounts of water until everything dissolves. The additional water will cause the solution to heat up, which helps dissolve everything, too.