That was me at the counter. The sender is the originator of the message. They have a thought, a feeling, or a deep desire for caffeine. (Or a muffin, apparently.) Everything begins here.
The sender’s job is to encode that thought. That means turning the abstract idea—“I want that drink space”—into a concrete message. My encoding was sloppy. I used the wrong words. Pro tip: If you want a coffee, maybe don’t point at the baked goods while saying “coffee.” Lesson learned.