The percentage of potential extract you actually get from your mash is called efficiency.
A good working number is 70%, although as you brew more you start to know how your system works and can adjust the number accordingly.
Now if we go back to sucrose, 1 pound of it contributes 46 points of sugar when added to one gallon of water. Another way of saying this is that it gives 46 ppg (points per pound per gallon).
All else derives from this, so before going any further let’s convert it to pkgl (points per kilogram per litre) with the conversion factor 8.345.