That is calculated in this calculation, so you just need that amount extra in to get it green. That's why you have to check just after consumption.
no its not calculated.
Lets make it easy and we say with 20000 Tons its yellow, short before consumption you take a look and see 24000 Tons with 20% you will see after consumption that 800 Tons missing so you will think when we have 24800 Tons its green but you need 25000 Tons for green.