I tested it today. Was playing Resident Evil, then went to Home screen, closed RE and put console to sleep at 01:30am at 53%. At 18:30pm I woke it up at 46%. So another ~10% per 24h. The running game or not in the background while sleep does not matter at all.This means you hold a charge on sleep for 1.4 weeks as opposed to the projected 2.4 which is nearly 2x the rate over previous benchmarks.
You may want to try again without software running in the background next time (i.e. Mario Kart) and see if that rate decreases any. Assuming you are using SX OS and since it isn't open source, we can't really see what any of the patches are doing in the background. I'm curious if that could be contributing to the drain as well.