Pretty self explanatory. I forgot to fully close the game, and when I got back this morning, it said I was off for 2 seconds. (This has happened before, too.)
I also double checked just now, and yeah. Enter to clear idle time, return to main menu, wait as long as you want, and return to the game. Only two seconds offline.
#staying on title screen maxes idle time at 2-3 seconds
merry falcon
runic pier