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Make a right click with your mouse on the area from which you want to deduct an area
Choose “Subtract from area” in the choices that appear
Click on the first corner of the area you want to deduct from the first area
Click on the second corner of the area you want to deduct
Click on the Third corner of the area you want to deduct
Click on the fourth corner of the area you want to deduct and repeat until the surface you want to deduct is all scratched out of the plan
Click on the “Stop” button when you are finish deducting the area from your takeoff