I'm amazed no one knows anything about this. Here is the "official" answer from a friend at TG:
Our procedure depends on meal and aircraft type.
If we serve breakfast, we start from each galley. Normally we have 2 galleys(in Economy Class) -front and back. That means the front galley will start from the front to middle and the back galley will start from the back to middle.
For lunch and dinner we start from middle to front and middle to back. For example NRT, when we use 777 aircraft so we start from around row 44-45. For HKG, it depends on the aircraft. If we use 333 we start from the middle (lavatory area) back to each galley for lunch and dinner.
It's a pleasure to answer.
This basically explains it all. If you're seated in the front section of Y (Row 31), you will be served last during lunch and dinner since they start from "middle to front", etc.