When you take the Standard quantity allowed and then subtract the Less actual quantity to get the difference. How do you get the Less actual quantity?

The actual quantity is what the company ACTUALLY used.
So if the company used 1,043 Litres to produce their product, that is the ACTUAL amount. Now, they could have budgeted for only 1,000 L or 1,300 L, but the ACTUAL is 1,043 Litres.