See, this can be done logically. Pour all the cups into a single large vessel. Then calculate the volume of coffee in each cup. Now, multiply that amount with 64, to get the volume of coffee in the large vessel. Now, you know the volume of the coffee in the large vessel.
Now, divide that much volume by 10, and then pour that much amount of coffee individually.
For example, let amount of coffee in each cup be 1 litre, so in 64 cups, it is 64 litre. Now, each one will get 64/10 = 6.4 litre.