"Off" is obvious - the box never goes into standby mode.
"Low" goes into standby after 90 minutes between 11 pm to 5 am, and 10 am to 5 pm.
"Medium" goes into standby after 120 minutes between 11 pm to 6 am.
"High" goes into standby after 180 minutes anytime at all.
It seems to me that "Low" power saving mode does more power saving than "Medium", as there are 13 hours of the day where it can go standby. "Medium" only has 7 hours to do so; moreover, it waits two hours first, rather than an hour and a half. "High" at least goes standby any time in 24 hours, but waits 3 hours before doing so.
Can others with a clearer understanding point out what I'm missing in the description?