It my understanding that as long as it turns bright red/pink, you're set. I also take into account that they say if you add 2 and it's still clear (when testing super high levels), that you just need to add another scoop until it turns red. I think I read in another post about this; that's where I first got it. I'm sure if it's not right, one of the mods or chem geek will let us know