It does not have to be precise, sbhikes. This isn't magic. You want to signal to your body first thing that it's going to be fed, and start the circadian rhythm off with this signal. It needs to happen soon after waking, and if you don't put an end point on it, people will put it off forever. Dr. K's endpoint is 30m. People are gonna whine and push it and say it's not enough, but as long as you are reasonably close with very few exceptions, it'll do the trick.
I did a sugar addiction program where the end point was 1hr, and people whined and pushed it and said that wasn't enough, either, so you just gotta pick an endpoint and go with it. Do it every day, with exceptions truly rare. It's totally worth it if your body needs it.