The reason for the 1 L (1 US qt) sparge volume difference between the App and G30 instructions, is that the basic formula printed in our instructions doesn't take into account if you are using a 220V or 110V version G30.
Because the 110V heater version has less power capacity than the 220V version (1600W vs 2000W), the boil evaporation rate is less (2 L (2.1 US qt) per hour instead of 3 L (3.2 US qt) per hour).
So for a 60-minute boil, with the 110V unit, you have to sparge with 1 L (1 US qt) less, because you lose 1 L (1 US qt) less during boil-off.
For more precise results, please see our calculators online or use the app.
The printed formula in the G30 instructions is to show you mostly, how the calculation works, however, it will differ depending on which unit you have.