Sodium hydroxide is lye, it's added in very small amounts to keep the pH high and increase the storage life of the bleach. That's not a problem, but the "Fabric Protection" is. Unfortunately that's been popping up in a lot of bleach products in the past few years and it isn't something you want to build up in your water.
If you've already purchased it, it shouldn't hurt to use a gallon of it. You'll want to avoid it in the future, however.