I find there is no mileage in worrying about this. I think the "When you first get out of bed rule" is probably meant for people who are otherwise healthy. The fact that I could apply that rule three or four times a night is something I feel I don't want to bother DN with.
When she asks at what time I took the sample I just tell her the time of the last time, in the night, I had a pee. Saves a lot of debate.