I just pop the 250mg pill into the beak. No weighing, no measuring, no cutting. If I had bantams or were I to treat a baby chick, I would be more precise. But a three to five pound adult chicken has responded well to my "casual" administrations.
There is a "range" that can be given, and I think it's 100-150 mg/kg, and I do believe that it's meant to be given at least twice a day.