I can understand the confusion.
You obviously know what 'menu' means and so I presume you also know 'meal'.
HOWEVER...in McDonal'ds restaurant, that illuminated plastic board overhead in front of you behind the counter is the menu. You will see individual items listed, and the prices; but also on display are complete meals for a reduced price - a Cheeseburger, fries and a shake. I think these 'complete meals' are termed 'value meals' and are pictured in their own separate box on the illuminated display, and numbered. You ask for a No.6 etc. So, if McChicken, fries and a coke is a No.2, then asking for the "McChicken menu", you have said the name of an individual item, and that's what he thinks you want - if you want the complete meal, he expects you to ask for a No.2.