It’s 4 hours, 8 hours, 23 hours, 47 hours to guru. That’s 3 days 10 hours. That’s the minimum time to guru the radicals. But all items reach guru in that amount of time so, that’ll unlock the last few kanji you need to push you into 90% guru for kanji, and take another 3 days 10 hours.
Yes, you do need to get 100% of reviews correct for those radicals and the 2nd wave kanji.
But the other 30 or so kanji you could get wrong for 3 days straight and not impact your minimum level up time. They just have to be done before 6 days 20 hours is up. You can wait a long time to do those lessons too.
And now that lessons don’t require a script to be ordered, you really don’t need any scripts or special effort to do the minimum time.
EDIT: Additionally, you have an hour of leeway whenever a review appears for it to be done “on time.” Say a review shows up at 1:00. As long as you do it by 1:59 it counts as having been done by 1:00. It rolls back to the start of whatever hour you’re on.
