Yes, "How much greater" means subtraction.you subtract the smaller number from the larger one when you want to find out the difference between two numbers. Example:
If you have 50 apples and I have 10 apples, you want to know how much greater your amount is than mine.
You would subtract: 50 apples - 10 apples = 40 apples.
So, your amount is 40 apples greater than mine.