Oh, a bit more math. Smart Lithium Ion batteries discharge at about 10% per month, so actual "off" discharge should be more like .3-.4% per day (unless there is some kind of other drain in there). The "sleep" discharge should be that, plus whatever the nook ST is using to keep monitoring the n button (probably no current used until the button is hit) and keeping the memory state (as I mentioned, 1-2mw).
So really, sleep discharge should be more like 1% per day, including the battery self discharge on the high end.
Of course as I am finding, the battery meter is not the most accurate thing in the world when it comes to gauging the true state of the battery charge on these things.