Final answer:
The reflux procedure should be timed after all the necessary steps have been completed, as shown in the example given.
Step-by-step explanation:
The reflux procedure should be timed after the tube is pushed down the throat, into the stomach, and into the upper part of the small intestine. Once all the necessary steps have been completed, the timing for reflux can start. In the provided example, the duodenal secretions were analyzed over a period of about two hours after the administration of secretin.