My Starbucks Idea

There is a website where one may suggest improvements to Starbucks. This is what I posted:

Three lines, labeled "1,2, 3" printed inside the cup indicate the level to which the customer would like the cup filled. A customer would say "I'd like a tall coffee. Fill it to 3, please."

This would eliminate the huge amount of wasted coffee that gets poured into the trash immediately upon purchase. (Surely you have all noticed this.)

This would also eliminate the ambiguous question and response concerning whether or not the customer wants "room" or not.

It would also speed up the purchase process. Surely you have noticed the number of times that a customer, upon receiving the order, hands it back immediately, asking the barista or cashier to add more coffee.

I'm assuming that there is a soy-based ink that is non-toxic and would not alter the flavor of the coffee.