Hi janeydee,
Guess it depends how impatient you are! You could set it for day 5, but you'd still be a week out, and welshgems right, you could miss your peak. Also it could affect the future months and when it starts asking you for sticks.
If you can't wait, I'd set it for day 5 as soon as you can, think it'll ask for sticks on its day 6, if you don't get lucky in this month, fully reset the machine before starting next month. It won't remember your half month then.