Dishes are served in the middle of the table. When you want to pick some food from a dish, you should rotate the table clockwise.
Beware: you should first mind that nobody picks up food before rotating the table.
I ask myself where does this custom come from?
No Chinese I met could explain the origin of the clockwise rotation.
The table rotation mecanism or lazy Susan was probably invented in the United Kingdom in the 18th century.
It could be that the clockwise direction of the rotation initially copies a clock?
It could be that the rotation matches ying and yang rotation, that is clockwise?