Thanks for all the input. I guess I was a shot short on the 20oz. I have a triple shot and double shot grinder but no quadruple shot. I guess that hasn't been invented yet lol. I will do two doubles.
From my experience, this is what I have found to be pretty standard. I drink Americanos and always check when I am ordering mine to make sure there are no surprises. It also serves as a good reminder to the barista who maybe used to making lattes all day long and might short me a shot.
12 oz - 2 shots
16 oz - 3 shots
20 oz - 4 shots