I agree with Funky-King. I use 2ml of bac water for every 5mg of Cagri. Makes the math simple. 0.2ml, or 20 units, equals 0.5mg. 10 units for 0.25mg. 5 units for 0.125mg.
If you only used 1ml of bac water, then you'd be at 2.5 units for a 0.125 dose, which would be difficult to measure correctly.