Sleep question for the BABYWISE moms

I’m about halfway through Babywise and have a question for all moms who used this method. For nap times, the book talks about letting your baby cry a bit (e.g., 15 mins before checking on them) so they hopefully put themselves asleep (assuming all other needs are met). I have a 5 week old and 15 minutes seems like a long time to let him try to put himself to sleep if he’s crying. I’m assuming they’re referring to older babies but I’m curious how other moms implemented the Babywise nap and bedtime philosophies with their newborns. Picture just because I think my baby’s cute ☺️